V62/09616-01XE [TI]

增强型产品 4:1 高速多路复用器 | D | 14 | -55 to 125;
V62/09616-01XE
型号: V62/09616-01XE
厂家: TEXAS INSTRUMENTS    TEXAS INSTRUMENTS
描述:

增强型产品 4:1 高速多路复用器 | D | 14 | -55 to 125

开关 信号电路 复用器 复用器或开关
文件: 总24页 (文件大小:853K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
4:1 HIGH-SPEED MULTIPLEXER  
1
FEATURES  
APPLICATIONS  
Video Router  
LCD and Plasma Display  
High Speed PGA  
2
500-MHz Small-Signal Bandwidth  
500-MHz, 2-VPP Bandwidth  
0.1-dB Gain Flatness to 120 MHz  
10-ns Channel-Switching Time  
Low Switching Glitch: 40 mVPP  
2300-V/µs Slew Rate  
Drop-In Upgrade to AD8174  
SUPPORTS DEFENSE, AEROSPACE,  
AND MEDICAL APPLICATIONS  
0.035%/0.005° Differential Gain, Phase  
Quiescent Current = 10.6 mA  
1.1-mA Quiescent Current in Shutdown Mode  
Controlled Baseline  
One Assembly/Test Site  
One Fabrication Site  
Available in Military (–55°C/125°C),  
Temperature Range(1)  
88-dB Off Isolation in Disable or Shutdown  
(10 MHz)  
Extended Product Life Cycle  
Extended Product-Change Notification  
Product Traceability  
(1) Additional temperature ranges available - contact factory  
DESCRIPTION  
The OPA4872 offers a very wideband 4:1 multiplexer in an SO-14 package. Using only 10.6 mA, the OPA4872  
provides a user-settable output amplifier gain with greater than 500-MHz large-signal bandwidth (2 VPP). The  
switching glitch is improved over earlier solutions using a new (patented) input stage switching approach. This  
technique uses current steering as the input switch while maintaining an overall closed-loop design. The  
OPA4872 exhibits an off isolation of 88dB in either Disable or Shutdown mode. With greater than 500-MHz  
small-signal bandwidth at a gain of 2, the OPA4872 gives a typical 0.1-dB gain flatness to greater than 120 MHz.  
System power may be optimized using the chip-enable feature for the OPA4872. Taking the chip enable (EN)  
line high powers down the OPA4872 to less than 3.4 mA total supply current. Further power reduction to 1.1mA  
quiescent current can be achieved by bringing the shutdown (SD) line high. Muxing multiple OPA4872s outputs  
together, then using the chip enable to select which channels are active, increases the number of possible  
inputs.  
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas  
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.  
2
All trademarks are the property of their respective owners.  
UNLESS OTHERWISE NOTED this document contains  
PRODUCTION DATA information current as of publication date.  
Products conform to specifications per the terms of Texas  
Instruments standard warranty. Production processing does not  
necessarily include testing of all parameters.  
Copyright © 2008, Texas Instruments Incorporated  
OPA4872-EP  
SBOS444DECEMBER 2008........................................................................................................................................................................................... www.ti.com  
+5V  
50W  
OPA695  
G = 1V/V  
-5V  
+5V  
523W  
50W  
IN0  
+5V  
OPA4872  
SD  
EN  
50W  
OPA695  
G = 2V/V  
-5V  
IN1  
IN2  
511W  
50W  
511W  
523W  
+5V  
To 50W Load  
50W  
523W  
OPA695  
G = 4V/V  
Logic  
-5V  
453W  
IN3  
A0 A1  
-5V  
149W  
+5V  
50W  
OPA695  
G = 8V/V  
-5V  
402W  
57.6W  
2-Bit, High-Speed PGA, Greater Than 300MHz Channel Bandwidth  
2
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Copyright © 2008, Texas Instruments Incorporated  
Product Folder Link(s): OPA4872-EP  
OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with  
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.  
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more  
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.  
ORDERING INFORMATION(1)  
SPECIFIED  
PACKAGE  
TEMPERATURE  
RANGE  
PACKAGE  
MARKING  
ORDERING  
NUMBER  
TRANSPORT  
MEDIA, QUANTITY  
PACKAGE-LEAD  
DESIGNATOR(2)  
SO-14  
D
–55°C to 125°C  
OPA4872M  
OPA4872MDREP  
Tape and Reel, 2500  
(1) For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI  
web site at www.ti.com.  
(2) Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available at  
www.ti.com/sc/package.  
ABSOLUTE MAXIMUM RATINGS(1)  
Over operating free-air temperature range, unless otherwise noted.  
OPA4872  
UNIT  
Power supply  
±6.5  
V
Internal power dissipation  
See Thermal Characteristics  
Input voltage range  
±VS  
–65 to +125  
+260  
V
°C  
°C  
°C  
°C  
V
Storage temperature range  
Lead temperature (soldering, 10s)  
Junction temperature (TJ)  
+150  
Junction temperature: continuous operation, long-term reliability  
Human body model (HBM)  
+140  
1500  
ESD rating  
Charged device model (CDM)  
Machine model (MM)  
1000  
V
200  
V
(1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may  
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond  
those specified is not implied.  
PIN CONFIGURATION  
SO-14  
Top View  
OPA4872  
V+  
IN0  
14  
13  
1
2
3
4
5
6
7
OUT  
GND  
IN1  
12 FB  
11 SD  
10 EN  
GND  
IN2  
9
8
A1  
A0  
V-  
IN3  
Copyright © 2008, Texas Instruments Incorporated  
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3
Product Folder Link(s): OPA4872-EP  
 
OPA4872-EP  
SBOS444DECEMBER 2008........................................................................................................................................................................................... www.ti.com  
ELECTRICAL CHARACTERISTICS: VS = ±5 V  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
MIN/MAX OVER  
TYP  
TEMPERATURE  
–55°C to  
MIN/  
MAX  
TEST  
PARAMETER  
CONDITIONS  
+25°C  
+25°C(2)  
+125°C(3)  
UNITS  
LEVEL(1)  
AC PERFORMANCE  
Small-signal bandwidth  
Bandwidth for 0.1 dB flatness  
Large-signal bandwidth  
Slew rate  
VO = 500 mVPP, RL = 150 Ω  
VO = 500 mVPP, RL = 150 Ω  
VO = 2 VPP, RL = 150 Ω  
4 V step  
500  
120  
500  
2300  
1.25  
15  
MHz  
MHz  
MHz  
V/µs  
ns  
min  
typ  
B
C
B
B
B
C
B
B
min  
min  
max  
typ  
Rise time and fall time  
Settling time  
4 V step  
to 0.05%  
to 0.1%  
2 V step  
ns  
2 V step  
14  
ns  
max  
max  
Channel switching time  
Harmonic distortion  
10  
ns  
G = +2 V/V, f = 10 MHz, VO = 2 VPP  
RL = 150 Ω  
2nd-harmonic  
-60  
-78  
dBc  
dBc  
max  
max  
max  
max  
max  
typ  
B
B
B
B
B
C
C
C
C
3rd-harmonic  
RL = 150 Ω  
Input voltage noise  
f > 100 kHz  
4.5  
nV/Hz  
pA/Hz  
pA/Hz  
%
Noninverting input current noise  
Inverting input current noise  
Differential gain  
f > 100 kHz  
4.0  
f > 100 kHz  
19  
G = +2 V/V, PAL, VO = 1.4 VP  
G = +2 V/V, PAL, VO = 1.4 VP  
Three channels driven at 5 MHz, 1 VPP  
Three channels driven at 30 MHz, 1 VPP  
0.035  
0.005  
-80  
Differential phase  
°
typ  
All hostile crosstalk, input-referred  
dB  
typ  
-66  
dB  
typ  
DC PERFORMANCE  
Open-loop transimpedance (ZOL  
)
VO = 0 V, RL = 100 Ω  
VCM = 0 V  
103  
±1  
92  
±5  
60  
±10.5  
±30  
kΩ  
mV  
min  
max  
max  
max  
max  
max  
max  
max  
A
A
B
A
A
B
A
B
Input offset voltage  
Average Input offset voltage drift  
Input offset voltage matching  
VCM = 0 V  
µV/°C  
mV  
VCM = 0 V  
±1  
±4  
±5  
±10.5  
±20  
Noninverting input bias current  
VCM = 0 V  
±14  
µA  
Average noninverting input bias current  
Inverting bias current  
Average inverting input bias current  
INPUT  
VCM = 0 V  
±48  
nA/°C  
µA  
VCM = 0 V  
±4  
±18  
±35  
VCM = 0 V  
±125  
nA/°C  
Common-mode input range (CMIR)  
Common-mode rejection ratio (CMRR)  
Input resistance  
Each noninverting input  
±2.7  
56  
±2.55  
50  
±2.4  
43  
V
min  
min  
A
A
VCM = 0 V, input-referred, noninverting input  
dB  
Noninverting  
Channel enabled  
open loop  
2.5  
70  
MΩ  
typ  
typ  
C
C
Inverting  
Input capacitance  
Noninverting  
Channel selected  
Channel deselected  
Chip disabled  
0.9  
0.9  
0.9  
pF  
pF  
pF  
typ  
typ  
typ  
C
C
C
OUTPUT  
Output voltage swing  
R
L 1 kΩ  
±4  
±3.9  
±3.55  
±48  
±3.55  
±3.35  
±38  
V
V
min  
min  
min  
typ  
A
A
A
C
C
RL = 150 Ω  
VO = 0 V  
±3.7  
±75  
Output current  
mA  
mA  
Short-circuit output current  
Closed-Loop output impedance  
Output shorted to ground  
G = +2 V/V, f 100 kHz  
±100  
0.03  
typ  
(1) Test levels: (A) 100% tested at +25°C. Over temperature limits set by characterization and simulation. (B) Limits set by characterization  
and simulation. (C) Typical value only for information.  
(2) Junction temperature = ambient for +25°C tested specifications.  
(3) Junction temperature = ambient at low temperature limit; junction temperature = ambient +9°C at high temperature limit for over  
temperature specifications.  
4
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Product Folder Link(s): OPA4872-EP  
OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
ELECTRICAL CHARACTERISTICS: VS = ±5 V (continued)  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
MIN/MAX OVER  
TYP  
TEMPERATURE  
–55°C to  
MIN/  
MAX  
TEST  
PARAMETER  
CONDITIONS  
+25°C  
+25°C(2)  
3.6  
+125°C(3)  
4.3  
UNITS  
LEVEL(1)  
ENABLE (EN)  
Power-down supply current  
Disable time  
VEN = 0 V  
VIN = ±0.25 VDC  
3.4  
25  
6
mA  
ns  
max  
typ  
typ  
typ  
typ  
typ  
A
C
C
C
C
C
Enable time  
VIN = ±0.25 VDC  
ns  
Off isolation  
G = +2 V/V, f = 10 MHz  
88  
14  
2.5  
dB  
MΩ  
pF  
Output resistance in disable  
Output capacitance in disable  
DIGITAL INPUTS  
Maximum logic 0  
Minimum logic 1  
A0, A1, EN, SD  
0.8  
2.0  
40  
0.8  
2.0  
55  
V
max  
min  
max  
typ  
B
B
A
C
C
C
A0, A1, EN, SD  
V
Logic input current  
Output switching glitch  
A0 , A1, EN, SD, input = 0V each line  
Channel selection, at matched load  
Channel disable, at matched load  
Shutdown, at matched load  
32  
µA  
mV  
mV  
mV  
±20  
±40  
±40  
typ  
typ  
SHUTDOWN  
Shutdown supply current  
Shutdown time  
VSD = 0 V  
VIN = ±0.25 VDC  
1.1  
75  
15  
88  
14  
2.5  
1.3  
2.0  
mA  
ns  
max  
typ  
typ  
typ  
typ  
typ  
A
C
C
C
C
C
Enable time  
VIN = ±0.25 VDC  
ns  
Off isolation  
G = +2 V/V, f = 10 MHz  
dB  
MΩ  
pF  
Output resistance in shutdown  
Output capacitance in shutdown  
POWER SUPPLY  
Specified operating voltage  
Minimum operating voltage  
Maximum operating voltage  
Maximum quiescent current  
Minimum quiescent current  
±5  
V
V
typ  
min  
max  
max  
min  
min  
min  
C
B
A
A
A
A
A
±3.5  
±6.0  
11  
±3.5  
±6.0  
12.5  
8.25  
–42  
V
VS = ±5 V  
VS = ±5 V  
10.6  
10.6  
–56  
–57  
mA  
mA  
dB  
dB  
10  
(+PSRR)  
(–PSRR)  
Input-referred  
Input-referred  
–50  
–51  
Power-supply rejection ratio  
–43  
THERMAL CHARACTERISTICS  
Specified operating range, D package  
Thermal resistance, θJA  
D
–55 to +125  
80  
°C  
typ  
typ  
C
C
Junction-to-ambient  
SO-14  
°C/W  
Copyright © 2008, Texas Instruments Incorporated  
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Product Folder Link(s): OPA4872-EP  
OPA4872-EP  
SBOS444DECEMBER 2008........................................................................................................................................................................................... www.ti.com  
TYPICAL CHARACTERISTICS  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
SMALL-SIGNAL FREQUENCY RESPONSE  
SMALL-SIGNAL FREQUENCY RESPONSE  
7
6
5
4
3
2
1
0
0.3  
6
3
G = +1V/V  
VO = 500mVPP  
Bandwidth  
0.2  
0.1  
0
Normalized  
0
Flatness  
-3  
-6  
-9  
-12  
G = +2V/V  
-0.1  
-0.2  
-0.3  
-0.4  
VO = 500mVPP  
RL = 150W  
G = +4V/V  
G = +2V/V  
1M  
10M  
100M  
Frequency (Hz)  
1G  
1M  
10M  
100M  
Frequency (Hz)  
Figure 2.  
1G 2G  
Figure 1.  
LARGE-SIGNAL FREQUENCY RESPONSE  
NONINVERTING PULSE RESPONSE  
7
6
5
4
3
2
1
0
0.5  
2.5  
RL = 150W  
G = +2V/V  
0.4  
0.3  
2.0  
VO = 2VPP  
Large-Signal 4VPP  
Right Scale  
1.5  
0.2  
1.0  
VO = 1VPP  
Small-Signal 0.4VPP  
Left Scale  
0.1  
0.5  
VO = 0.5VPP  
0
0
-0.1  
-0.2  
-0.3  
-0.4  
-0.5  
-0.5  
-1.0  
-1.5  
-2.0  
-2.5  
VO = 4VPP  
-1  
-2  
-3  
0
200M  
400M  
600M  
800M  
1G  
Time (10ns/div)  
Frequency (Hz)  
Figure 3.  
Figure 4.  
RECOMMENDED RS vs CAPACITIVE LOAD  
FREQUENCY RESPONSE vs CAPACITIVE LOAD  
100  
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
8
7
CL = 10pF  
6
5
4
VI  
3
75W  
2
CL = 22pF  
RS  
+
75W  
75W  
75W  
1
VO  
1kW(1)  
-
CL  
523W  
0
CL = 47pF  
523W  
-1  
-2  
-3  
NOTE: (1) Optional.  
CL = 100pF  
1
10  
Capacitive Load (pF)  
Figure 5.  
100  
1000  
1
10  
100  
300  
Frequency (MHz)  
Figure 6.  
6
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Product Folder Link(s): OPA4872-EP  
 
OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
TYPICAL CHARACTERISTICS (continued)  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
HARMONIC DISTORTION vs LOAD RESISTANCE  
HARMONIC DISTORTION vs SUPPLY VOLTAGE  
-55  
-60  
-65  
-70  
-75  
-80  
-85  
-90  
-95  
-55  
-60  
-65  
-70  
-75  
-80  
-85  
-90  
2nd-Harmonic  
VO = 2VPP  
f = 5MHz  
2nd-Harmonic  
3rd-Harmonic  
3rd-Harmonic  
VO = 2VPP  
RL = 150W  
dBc = dB Below Carrier  
dBc = dB Below Carrier  
f = 5MHz  
2.5  
3.0  
3.5  
4.0  
4.5  
5.0  
5.5  
6.0  
100  
1k  
Supply Voltage (±VS)  
Load Resistance (W)  
Figure 7.  
Figure 8.  
HARMONIC DISTORTION vs FREQUENCY  
HARMONIC DISTORTION vs OUTPUT VOLTAGE  
-40  
-45  
-50  
-55  
-60  
-65  
-70  
-75  
-80  
-85  
-90  
-95  
-50  
-55  
-60  
-65  
-70  
-75  
-80  
-85  
-90  
-95  
-100  
VO = 2VPP  
RL = 150W  
RL = 150W  
f = 5MHz  
2nd-Harmonic  
2nd-Harmonic  
3rd-Harmonic  
3rd-Harmonic  
dBc = dB Below Carrier  
dBc = dB Below Carrier  
1
10  
100  
0.5  
1.5  
2.5  
3.5  
4.5  
5.5  
6.5  
7.5  
Frequency (MHz)  
Output Voltage Swing (VPP  
)
Figure 9.  
Figure 10.  
DISABLE AND SHUTDOWN FEEDTHROUGH vs  
FREQUENCY  
OUTPUT VOLTAGE AND CURRENT LIMITATIONS  
6
5
-20  
-30  
1W Internal  
Power Limit  
Input-referred  
4
-40  
100W Load  
3
-50  
2
Shutdown Feedthrough  
1
-60  
50W Load  
25W Load  
0
-70  
-1  
-2  
-3  
-4  
-5  
-80  
Disable Feedthrough  
1W Internal  
Power Limit  
-90  
-100  
-110  
-200  
-100  
0
100  
200  
300  
1M  
10M  
100M  
Frequency (Hz)  
1G  
Output Current (mA)  
Figure 11.  
Figure 12.  
Copyright © 2008, Texas Instruments Incorporated  
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Product Folder Link(s): OPA4872-EP  
 
OPA4872-EP  
SBOS444DECEMBER 2008........................................................................................................................................................................................... www.ti.com  
TYPICAL CHARACTERISTICS (continued)  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
CHANNEL-TO-CHANNEL SWITCHING  
CHANNEL-TO-CHANNEL SWITCHING GLITCH  
75  
50  
0.75  
0.50  
0.25  
0
At Matched Load  
25  
Output Voltage  
0
-25  
-50  
-75  
-0.25  
-0.50  
-0.75  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
VIN_Ch0 = 200MHz, 0.7VPP  
VIN_Ch1 = 0VDC  
A0  
A0  
Time (10ns/div)  
Time (10ns/div)  
Figure 13.  
Figure 14.  
DISABLE/ENABLE TIME  
DISABLE/ENABLE SWITCHING GLITCH  
75  
50  
0.75  
0.50  
0.25  
0
At Matched Load  
25  
Output  
0
-25  
-50  
-75  
-0.25  
-0.50  
-0.75  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
VIN_Ch0 = 200MHz, 0.10VPP  
EN  
EN  
Time (10ns/div)  
Time (10ns/div)  
Figure 15.  
Figure 16.  
SHUTDOWN/START-UP TIME  
SHUTDOWN GLITCH  
75  
50  
0.75  
0.50  
0.25  
0
At Matched Load  
25  
Output  
0
-25  
-50  
-75  
-0.25  
-0.50  
-0.75  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
VIN_Ch0 = 200MHz, 0.7VPP  
SD  
SD  
Time (20ns/div)  
Time (20ns/div)  
Figure 17.  
Figure 18.  
8
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Product Folder Link(s): OPA4872-EP  
OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
TYPICAL CHARACTERISTICS (continued)  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
OPEN-LOOP TRANSIMPEDANCE GAIN AND PHASE vs  
ALL HOSTILE CROSSTALK vs FREQUENCY  
FREQUENCY  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
1M  
100k  
10k  
1k  
0
Input-referred  
< ZOL  
-45  
-90  
-135  
-180  
-225  
½ZOL  
½
100  
10  
10k  
100k  
1M  
10M  
100M  
1G  
1M  
10M  
100M  
Frequency (Hz)  
1G  
Frequency (Hz)  
Figure 19.  
Figure 20.  
CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY  
1M  
INPUT IMPEDANCE vs FREQUENCY  
100M  
10M  
1M  
Disabled  
100k  
Disabled (or Shutdown)  
10k  
1k  
Enabled  
100k  
10k  
1k  
100  
10  
1
Enabled  
10M  
0.1  
100  
100k  
1M  
100M  
1G  
10k  
100k  
1M  
10M  
100M  
1G  
Frequency (Hz)  
Frequency (Hz)  
Figure 21.  
Figure 22.  
PSRR vs FREQUENCY  
OUTPUT AND SUPPLY CURRENT vs TEMPERATURE  
15.00  
78.00  
76.75  
75.50  
74.25  
73.00  
71.75  
70.50  
69.25  
68.00  
60  
50  
40  
30  
20  
10  
0
13.75  
Input-referred  
12.50  
-PSRR  
Supply Current (IQ)  
11.25  
10.00  
8.75  
+PSRR  
+IOUT  
7.50  
6.25  
-IOUT  
5.00  
-50  
-25  
0
25  
50  
75  
100  
125  
1k  
10k  
100k  
1M  
10M  
100M  
1G  
Ambient Temperature (°C)  
Frequency (Hz)  
Figure 23.  
Figure 24.  
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TYPICAL CHARACTERISTICS (continued)  
At TA = +25°C, G = +2 V/V, RF = 523 , and RL = 150 , unless otherwise noted.  
TYPICAL DC DRIFT OVER TEMPERATURE  
INPUT VOLTAGE AND CURRENT NOISE  
2.0  
1.5  
9
8
7
6
5
4
3
2
1
0
-1  
300  
100  
1.0  
VOS  
Inverting Input Current Noise (19pA/ÖHz)  
0.5  
0
Ibn  
-0.5  
-1.0  
-1.5  
-2.0  
-2.5  
-3.0  
10  
Input Voltage Noise (4.5nV/ÖHz)  
Ibi  
Noninverting Input Current Noise (4pA/ÖHz)  
1
-50  
-25  
0
25  
50  
75  
100  
125  
10  
100  
1k  
10k  
100k  
1M  
10M  
Ambient Temperature (°C)  
Frequency (Hz)  
Figure 26.  
Figure 25.  
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APPLICATION INFORMATION  
input of a current feedback amplifier. Depending on  
the logic applied to channel control pins A0 and A1,  
one switch is on at all times. Figure 27 represents the  
OPA4872 in this configuration. The truth table for  
channel selection is shown in Table 1.  
WIDEBAND MULTIPLEXER OPERATION  
The OPA4872 gives a new level of performance in  
wideband multiplexers. Figure 27 shows the  
dc-coupled, gain of +2 V/V, dual power-supply circuit  
used as the basis of the ±5-V Electrical  
Characteristics and Typical Characteristic curves. For  
test purposes, the input impedance is set to 75 with  
a resistor to ground and the output impedance is set  
to 75 with a series output resistor. Voltage swings  
reported in the specifications are taken directly at the  
input and output pins while load powers (in dBm) are  
defined at a matched 75-load. For the circuit of  
Figure 27, the total effective load will be 150 ||  
1046 = 131 . Logic pins A0 and A1 control which  
of the four inputs is selected while EN and SD allow  
for power reduction. One optional component is  
included in Figure 27. In addition to the usual  
power-supply decoupling capacitors to ground, a  
0.01-µF capacitor is included between the two  
power-supply pins. In practical printed circuit board  
(PCB) layouts, this optional added capacitor typically  
improves the 2nd-harmonic distortion performance by  
3 dB to 6 dB for bipolar supply operation.  
Table 1. TRUTH TABLE  
A0  
0
A1  
0
EN  
0
SD  
0
VOUT  
IN0  
1
0
0
0
IN1  
IN2  
0
1
0
0
1
1
0
0
IN3  
X
X
X
X
1
0
High-Z, IQ = 3.4 mA  
High-Z, IQ = 1.1 mA  
X
1
The OPA4872 is in disable mode, with a quiescent  
current of 3.4mA typical, when the EN pin is set to  
0V. After being placed in disable mode, the OPA4872  
is fully enabled in 6ns. For further power savings, the  
SD pin can be used. Setting the SD pin to 5V places  
the device in shutdown mode with a standing  
quiescent current of 1.1 mA. Note that in this  
shutdown mode, the OPA4872 requires 15ns to be  
fully powered again. The truth table for disable and  
shutdown modes can be found in Table 1.  
Even though the internal architecture of the OPA4872  
includes current steering, it is advantageous to look  
at it as four switches looking into the noninverting  
+5V  
0.1mF  
6.8mF  
+
OPA4872  
SD  
EN  
IN0  
VIN0  
75W  
IN1  
VIN1  
75W  
75W  
VOUT  
To 75W Load  
IN2  
523W  
VIN2  
75W  
523W  
IN3  
VIN3  
A0  
A1  
75W  
Optional  
0.1mF  
6.8mF  
0.01mF  
+
-5V  
Figure 27. DC-Coupled, G = +2V/V Bipolar Specification and Test Circuit (Channel 0 Selected)  
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2-BIT HIGH-SPEED PGA  
When channel 0 is selected, the overall gain to the  
matched load of the OPA4872 is 0dB. When channel  
1 is selected, this circuit delivers 6 dB of gain to the  
matched load. When channel 2 is selected, this circuit  
delivers 12 dB of gain to the matched load. When  
channel 3 is selected, this circuit delivers 18 dB of  
gain to the matched load.  
The OPA4872 can be used as a 2-bit, high-speed  
programmable gain amplifier (PGA) when used in  
conjunction with another amplifier. Figure 28 shows  
one OPA695 used in series with each OPA4876 input  
and configured with gains of +1 V/V, +2 V/V, +4 V/V,  
and +8 V/V, respectively.  
+5V  
50W  
OPA695  
G = 1V/V  
-5V  
+5V  
523W  
50W  
IN0  
+5V  
OPA4872  
SD  
EN  
50W  
OPA695  
G = 2V/V  
-5V  
IN1  
IN2  
511W  
50W  
511W  
523W  
+5V  
To 50W Load  
50W  
523W  
OPA695  
G = 4V/V  
Logic  
-5V  
453W  
IN3  
A0 A1  
-5V  
149W  
+5V  
50W  
OPA695  
G = 8V/V  
-5V  
402W  
57.6W  
Figure 28. 2-Bit, High-Speed PGA, Greater Than 300MHz Channel Bandwidth  
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2-BIT, HIGH-SPEED ATTENUATOR  
8-TO-1 VIDEO MULTIPLEXER  
In contrast to the PGA,  
a
two-bit high-speed  
Two OPA4872s can be used together to form an  
8-input video multiplexer. The multiplexer is shown in  
Figure 31.  
attenuator can be implemented by using an R-2R  
ladder together with the OPA4872. Figure 29 shows  
such an implementation.  
Channel 0 sees the full input signal amplitude, where  
as channel 1 sees 1/2 VIN, channel 2 see 1/4 VIN and  
channel 3 sees 1/8 VIN.  
OPA4872  
EN  
SD  
VIN  
OPA4872  
SD  
2R  
IN0  
EN  
RO = 69W  
R
2R  
523W  
IN1  
To 75W Load  
50W  
R
523W  
VOUT  
2R  
IN2  
523W  
To 50W Load  
Logic  
R
523W  
R
IN3  
Logic  
OPA4872  
EN  
A0 A1  
SD  
Figure 29. 2-Bit, High-Speed Attenuator,  
500MHz Channel Bandwidth  
4-INPUT RGB ROUTER  
RO = 69W  
523W  
Three OPA4872s can be used together to form a  
four-input RGB router. The router for the red  
component is shown in Figure 30. Identical stages  
would be used for the green and blue channels.  
523W  
Logic  
+5V  
OPA4872  
EN  
Figure 31. 8-to-1 Video Multiplexer  
SD  
R1  
When connecting OPA4872 outputs together,  
maintain a gain of +1V/V at the load. The OPA4872  
configuration shown is a gain of +6 dB; thus, the  
matching resistance must be selected to achieve  
–6 dB.  
R2  
75W  
Red Out  
523W  
The set of equations to solve is shown in Equation 1  
and Equation 2. Here, the impedance of interest is  
75 .  
R3  
To 75W Load  
523W  
R4  
RO = ZO || (RO + RF + RG)  
RF  
Logic  
1 +  
= 2  
A0 A1  
RG  
(1)  
(2)  
-5V  
RF + RG = 1046W  
Figure 30. 4-Input RGB Router  
(Red Channel Shown)  
RF = RG  
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Solving for RO, with n devices connected together,  
results in Equation 3:  
OPERATING SUGGESTIONS  
SETTING RESISTOR VALUES TO OPTIMIZE  
BANDWIDTH  
75 ´ (n - 1) + 804  
241200  
[75 ´ (n - 1) + 804]2  
RO  
=
´
1 +  
- 1  
2
The output stage of the OPA4872 is  
a
current-feedback op amp, meaning it can hold an  
almost constant bandwidth over signal gain settings  
with the proper adjustment of the external resistor  
values. This performance is shown in the Typical  
Characteristic curves; the small-signal bandwidth  
decreases only slightly with increasing gain. These  
curves also show that the feedback resistor has been  
changed for each gain setting. The resistor values on  
the feedback path can be treated as frequency  
response compensation elements while the ratio sets  
the signal gain of the feedback resistor divided by the  
gain resistor. Figure 32 shows the small-signal  
frequency response analysis circuit for a current  
feedback amplifier.  
(3)  
Results for n varying from 2 to 6 are given in Table 2.  
Table 2. Series Resistance vs  
Number of Parallel Outputs  
NUMBER OF OPA4872s  
RO ()  
69  
2
3
4
5
6
63.94  
59.49  
55.59  
52.15  
The two major limitations of this circuit are the device  
requirements for each OPA4872 and the acceptable  
return loss resulting from the mismatch between the  
load and the matching resistor.  
VI  
a
VO  
DESIGN-IN TOOLS  
RI  
Z(S) iERR  
DEMONSTRATION FIXTURE  
iERR  
RF  
A printed circuit board (PCB) is available to assist in  
the initial evaluation of circuit performance using the  
OPA4872. The fixture is offered free of charge as an  
unpopulated PCB, delivered with a user's guide. The  
summary information for this fixture is shown in  
Table 3.  
RG  
Figure 32. Recommended Feedback Resistor vs  
Noise Gain  
Table 3. OPA4872 Demonstration Fixture  
LITERATURE  
PACKAGE  
ORDERING NUMBER  
NUMBER  
The key elements of this current-feedback op amp  
model are:  
SO-14  
DEM-OPA-SO-1E  
SBOU045  
α Buffer gain from the noninverting input to the  
inverting input  
The demonstration fixture can be requested at the  
Texas Instruments web site at (www.ti.com) through  
the OPA4872 product folder.  
RI Buffer output impedance  
iERR Feedback error current signal  
MACROMODELS AND APPLICATIONS SUPPORT  
Z(s) Frequency-dependent  
transimpedance gain from iERR to VO  
open-loop  
Computer simulation of circuit performance using  
SPICE is often useful when analyzing the  
performance of analog circuits and systems. This  
practice is particularly true for video and RF amplifier  
circuits, where parasitic capacitance and inductance  
can have a major effect on circuit performance. A  
SPICE model for the OPA4872 is available through  
the Texas Instruments web site at www.ti.com. This  
model does a good job of predicting small-signal ac  
and transient performance under a wide variety of  
operating conditions. It does not do as well in  
predicting the harmonic distortion or dG/dP  
characteristics.  
The buffer gain is typically very close to 1.00 and is  
normally neglected from signal gain considerations. It  
will, however, set the CMRR for a single op amp  
differential amplifier configuration. For a buffer gain  
α < 1.0, the CMRR = –20 × log (1 – α) dB.  
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RI, the buffer output impedance, is a critical portion of  
the bandwidth control equation. RI for the OPA4872 is  
typically about 30 . A current-feedback op amp  
senses an error current in the inverting node (as  
opposed to a differential input error voltage for a  
voltage-feedback op amp) and passes this on to the  
output through an internal frequency dependent  
transimpedance gain. The Typical Characteristics  
show this open-loop transimpedance response. This  
open-loop response is analogous to the open-loop  
voltage gain curve for a voltage-feedback op amp.  
Developing the transfer function for the circuit of  
Figure 32 gives Equation 4:  
The OPA4872 is internally compensated to give a  
maximally flat frequency response for RF = 523 at  
NG = 2 on ±5-V supplies. Evaluating the denominator  
of Equation 5 (which is the feedback transimpedance)  
gives an optimal target of 663 . As the signal gain  
changes, the contribution of the NG × RI term in the  
feedback transimpedance will change, but the total  
can be held constant by adjusting RF. Equation 6  
gives an approximate equation for optimum RF over  
signal gain:  
RF = 663W - NG x RI  
(6)  
As the desired signal gain increases, this equation  
will eventually predict a negative RF. A somewhat  
subjective limit to this adjustment also can be set by  
holding RG to a minimum value of 20 . Lower values  
load both the buffer stage at the input and the output  
stage, if RF gets too low, actually decreasing the  
bandwidth. Figure 33 shows the recommended RF  
versus NG for ±5-V operation. The values for RF  
versus gain shown here are approximately equal to  
the values used to generate the Typical  
Characteristics. They differ in that the optimized  
values used in the Typical Characteristics are also  
correcting for board parasitics not considered in the  
simplified analysis leading to Equation 5. The values  
shown in Figure 33 give a good starting point for  
design where bandwidth optimization is desired.  
RF  
a 1+  
VO  
VI  
RG  
RF  
aNG  
RF + RI NG  
Z(S)  
=
=
RF + RI  
1+  
1+  
RG  
1+  
Z(S)  
where:  
RF  
= 1+  
NG  
RG  
(4)  
This formula is written in a loop-gain analysis format,  
where the errors arising from a noninfinite open-loop  
gain are shown in the denominator. If Z(S) were  
infinite over all frequencies, the denominator of  
Equation 4 would reduce to 1 and the ideal desired  
signal gain shown in the numerator would be  
achieved. The fraction in the denominator of  
Equation 4 determines the frequency response.  
Equation 5 shows this as the loop-gain equation:  
600  
550  
500  
450  
400  
350  
300  
250  
200  
150  
100  
Z(S)  
= Loop Gain  
RF + RI NG  
(5)  
If 20 × log(RF + NG × RI) were drawn on top of the  
open-loop transimpedance plot, the difference  
between the two calculations would be the loop gain  
at a given frequency. Eventually, Z(S) rolls off to equal  
the denominator of Equation 5, at which point the  
loop gain reduces to 1 (and the curves intersect).  
This point of equality is where the amplifier  
closed-loop frequency response given by Equation 4  
starts to roll off, and is exactly analogous to the  
frequency at which the noise gain equals the  
open-loop voltage gain for a voltage-feedback op  
amp. The difference here is that the total impedance  
in the denominator of Equation 5 may be controlled  
somewhat separately from the desired signal gain (or  
NG).  
0
5
10  
15  
20  
Noise Gain  
Figure 33. Feedback Resistor vs Noise Gain  
The total impedance going into the inverting input  
may be used to adjust the closed-loop signal  
bandwidth. Inserting a series resistor between the  
inverting input and the summing junction increases  
the feedback impedance (denominator of Equation 4),  
decreasing the bandwidth.  
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DRIVING CAPACITIVE LOADS  
VOSO_envelope = VOS ´ G ± Ibi x RF ± (RS ´ Ib) ´ G  
PSRR+  
± ½5 - (VS+)½ ´ 10-  
One of the most demanding, yet very common load  
conditions, is capacitive loading. Often, the capacitive  
load is the input of an analog-to-digital converter  
(ADC)—including additional external capacitance that  
may be recommended to improve ADC linearity. A  
high-speed device such as the OPA4872 can be very  
susceptible to decreased stability and closed-loop  
response peaking when a capacitive load is placed  
directly on the output pin. When the device open-loop  
output resistance is considered, this capacitive load  
introduces an additional pole in the signal path that  
can decrease the phase margin. Several external  
solutions to this problem have been suggested. When  
the primary considerations are frequency response  
flatness, pulse response fidelity, and/or distortion, the  
simplest and most effective solution is to isolate the  
capacitive load from the feedback loop by inserting a  
series isolation resistor between the amplifier output  
and the capacitive load. This isolation resistor does  
not eliminate the pole from the loop response, but  
rather shifts it and adds a zero at a higher frequency.  
The additional zero acts to cancel the phase lag from  
the capacitive load pole, thus increasing the phase  
margin and improving stability.  
20  
PSRR-  
±½-5 - (VS-)½ ´ 10-  
20  
(7)  
Where:  
RS: Input resistance seen by R0, R1, G0, G1, B0,  
or B1.  
Ib: Noninverting input bias current  
Ibi: Inverting input bias current  
G: Gain  
VS+: Positive supply voltage  
VS–: Negative supply voltage  
PSRR+: Positive supply PSRR  
PSRR–: Negative supply PSRR  
VOS: Input Offset Voltage  
Evaluating the front-page schematic, using  
a
worst-case, +25°C offset voltage, bias current and  
PSRR specifications and operating at ±6 V, gives a  
worst-case output equal to Equation 8:  
±10mV + 75W ´ ±14mA ´ 2  
50  
±½5 - 6½ ´ 10-  
20  
+523W ´ ±18mA  
±½-5 - (-6)½ ´ 10-  
51  
20  
The Typical Characteristics show the recommended  
RS versus capacitive load and the resulting frequency  
response at the load; see Figure 5. Parasitic  
capacitive loads greater than 2 pF can begin to  
degrade the performance of the OPA4872. Long PCB  
traces, unmatched cables, and connections to  
multiple devices can easily cause this value to be  
exceeded. Always consider this effect carefully, and  
add the recommended series resistor as close as  
possible to the OPA4872 output pin (see the Board  
Layout Guidelines section).  
=
±
29.2mV  
(8)  
DISTORTION PERFORMANCE  
The OPA4872 provides good distortion performance  
into a 150-load on ±5-V supplies. Relative to  
alternative solutions, it provides exceptional  
performance into lighter loads. Generally, until the  
fundamental signal reaches very high frequency or  
power levels, the 2nd harmonic dominates the  
distortion with a negligible 3rd harmonic component.  
Focusing then on the 2nd harmonic, increasing the  
load impedance directly improves distortion. Also,  
providing an additional supply decoupling capacitor  
(0.01 µF) between the supply pins (for bipolar  
operation) improves the 2nd-order distortion slightly  
(3 dB to 6 dB).  
DC ACCURACY  
The OPA4872 offers excellent dc signal accuracy.  
Parameters that influence the output dc offset voltage  
are:  
Output offset voltage  
Input bias current  
Gain error  
Power-supply rejection ratio  
Temperature  
In most op amps, increasing the output voltage swing  
increases harmonic distortion directly. The Typical  
Characteristics show the 2nd harmonic increasing at  
a little less than the expected 2X rate while the 3rd  
harmonic increases at a little less than the expected  
3X rate. Where the test power doubles, the 2nd  
harmonic increases only by less than the expected 6  
dB, whereas the 3rd harmonic increases by less than  
the expected 12 dB.  
Leaving both temperature and gain error parameters  
aside, the output offset voltage envelope can be  
described as shown in Equation 7:  
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NOISE PERFORMANCE  
EO  
=
ENI2 + (IBNRS)2 + 4kTRS NG2 + (IBIRF)2 + 4kTRFNG  
(
)
Ö
The OPA4872 offers an excellent balance between  
voltage and current noise terms to achieve low output  
noise. The inverting current noise (19 pA/Hz) is  
significantly lower than earlier solutions, while the  
input voltage noise (4.5 nV/Hz) is lower than most  
unity-gain stable, wideband, voltage-feedback op  
amps. As long as the ac source impedance looking  
out of the noninverting node is less than 100 , this  
current noise will not contribute significantly to the  
total output noise. The op amp input voltage noise  
and the two input current noise terms combine to give  
low output noise under a wide variety of operating  
conditions. Figure 34 shows the OPA4872 noise  
analysis model with all the noise terms included. In  
this model, all noise terms are taken to be noise  
voltage or current density terms in either nV/Hz or  
pA/Hz.  
(9)  
Dividing this expression by the noise gain (NG = (1 +  
RF/RG)) gives the equivalent input-referred spot noise  
voltage at the noninverting input, as shown in  
Equation 10.  
2
EO = ENI2 + (IBNRS)2 + 4kTRS +  
IBIRF 4kTRF  
+
(
)
Ö
NG  
NG  
(10)  
Evaluating these two equations for the OPA4872  
circuit and component values (see Figure 27) gives a  
total output spot noise voltage of 14.2 nV/Hz and a  
total equivalent input spot noise voltage of 7.1  
nV/Hz. This total input-referred spot noise voltage is  
higher than the 4.5-nV/Hz specification for the  
OPA4872 voltage noise alone. This voltage reflects  
the noise added to the output by the inverting current  
noise times the feedback resistor. If the feedback  
resistor is reduced in high-gain configurations, the  
total input-referred voltage noise given by  
Equation 10 approaches only the 4.5 nV/Hz of the  
op amp itself. For example, going to a gain of +10  
using RF = 178 gives a total input-referred noise of  
4.7 nV/Hz.  
ENI  
EO  
OPA4872  
RS  
IBN  
ERS  
RF  
Ö4kTRS  
Ö4kTRF  
IBI  
RG  
4kT  
RG  
20  
4kT = 1.6 x 10  
at 290K  
J
Figure 34. Op Amp Noise Analysis Model  
The total output spot noise voltage can be computed  
as the square root of the sum of all squared output  
noise voltage contributors. Equation 9 shows the  
general form for the output noise voltage using the  
terms shown in Figure 35.  
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THERMAL ANALYSIS  
load power. Quiescent power is simply the specified  
no-load supply current times the total supply voltage  
across the part. PDL depends on the required output  
signal and load; for a grounded resistive load, PDL is  
at a maximum when the output is fixed at a voltage  
equal to 1/2 of either supply voltage (for equal bipolar  
Heatsinking or forced airflow may be required under  
extreme operating conditions. Maximum desired  
junction temperature sets the maximum allowed  
internal power dissipation as discussed in this  
document. In no case should the maximum junction  
temperature be allowed to exceed +150°C.  
2
supplies). Under this condition PDL = VS /(4 × RL),  
where RL includes feedback network loading.  
Operating junction temperature (TJ) is given by TA  
+
Note that it is the power in the output stage and not in  
the load that determines internal power dissipation.  
PD × θJA. The total internal power dissipation (PD) is  
the sum of quiescent power (PDQ) and additional  
power dissipated in the output stage (PDL) to deliver  
-20  
en  
4kT = 1.6 x 10  
J
OPA4872  
at 290K  
RS  
ini  
VRS = Ö4kTRS  
eo  
RF  
VRF = Ö4kTRF  
4kT  
iin  
iRG  
RG  
Ö
RG  
Figure 35. OPA4872 Noise Analysis Model  
18  
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OPA4872-EP  
www.ti.com........................................................................................................................................................................................... SBOS444DECEMBER 2008  
As a worst-case example, compute the maximum TJ  
using an OPA4872ID in the circuit of Figure 27  
operating at the maximum specified ambient  
temperature of +85°C with its output driving a  
grounded 100-load to +2.5 V:  
Again, keep their leads and PCB trace length as short  
as possible. Never use wirewound type resistors in a  
high-frequency  
application.  
Other  
network  
components, such as noninverting input termination  
resistors, should also be placed close to the package.  
PD = 10V ´ 11.7mA + (52/[4 ´ (150W || 1046W)]) = 165mW  
d) Connections to other wideband devices on the  
board may be made with short direct traces or  
through onboard transmission lines. For short  
connections, consider the trace and the input to the  
next device as a lumped capacitive load. Relatively  
wide traces (50mils to 100mils) should be used,  
preferably with ground and power planes opened up  
around them.  
Maximum TJ = +85°C + (165mW ´ 80°C/W) = 98°C  
This worst-case condition does not exceed the  
maximum junction temperature. Normally, this  
extreme case is not encountered.  
BOARD LAYOUT GUIDELINES  
Estimate the total capacitive load and set RS from the  
plot of Figure 5. Low parasitic capacitive loads  
(greater than 5 pF) may not need an RS because the  
OPA4872 is nominally compensated to operate with a  
2-pF parasitic load. If a long trace is required, and the  
6dB signal loss intrinsic to a doubly-terminated  
transmission line is acceptable, implement a matched  
impedance transmission line using microstrip or  
stripline techniques (consult an ECL design handbook  
for microstrip and stripline layout techniques). A 50-Ω  
environment is normally not necessary on the board,  
Achieving  
optimum  
performance  
with  
a
high-frequency amplifier such as the OPA4872  
requires careful attention to board layout parasitics  
and external component types. Recommendations to  
optimize performance include:  
a) Minimize parasitic capacitance to any ac  
ground for all of the signal I/O pins. Parasitic  
capacitance on the output pin can cause instability;  
on the noninverting input, it can react with the source  
impedance to cause unintentional bandlimiting. To  
reduce unwanted capacitance, a window around the  
signal I/O pins should be opened in all of the ground  
and power planes around those pins. Otherwise,  
ground and power planes should be unbroken  
elsewhere on the board.  
and in fact,  
a higher impedance environment  
improves distortion as shown in the Distortion versus  
Load plot; see Figure 7. With a characteristic board  
trace impedance defined based on board material  
and trace dimensions, a matching series resistor into  
the trace from the output of the OPA4872 is used as  
well as a terminating shunt resistor at the input of the  
destination device. Remember also that the  
terminating impedance is the parallel combination of  
the shunt resistor and the input impedance of the  
destination device; this total effective impedance  
should be set to match the trace impedance. The  
high output voltage and current capability of the  
OPA4872 allow multiple destination devices to be  
handled as separate transmission lines, each with its  
own series and shunt terminations. If the 6-dB  
attenuation of a doubly-terminated transmission line  
b) Minimize the distance (< 0.25") from the  
power-supply pins to high frequency 0.1-µF  
decoupling capacitors. At the device pins, the  
ground and power plane layout should not be in close  
proximity to the signal I/O pins. Avoid narrow power  
and ground traces to minimize inductance between  
the pins and the decoupling capacitors. The  
power-supply connections (on pins 9, 11, 13, and 15)  
should always be decoupled with these capacitors.  
An optional supply decoupling capacitor across the  
two power supplies (for bipolar operation) improves  
2nd harmonic distortion performance. Larger (2.2 µF  
to 6.8 µF) decoupling capacitors, effective at lower  
frequency, should also be used on the main supply  
pins. These capacitors may be placed somewhat  
farther from the device and may be shared among  
several devices in the same area of the PCB.  
is  
unacceptable,  
a
long  
trace  
can  
be  
series-terminated at the source end only. Treat the  
trace as a capacitive load in this case and set the  
series resistor value as shown in Figure 5. This  
configuration does not preserve signal integrity as  
well as  
a doubly-terminated line. If the input  
impedance of the destination device is low, there will  
be some signal attenuation because of the voltage  
divider formed by the series output into the  
terminating impedance.  
c) Careful selection and placement of external  
components  
preserves  
the  
high-frequency  
performance of the OPA4872. Resistors should be  
a very low reactance type. Surface-mount resistors  
work best and allow a tighter overall layout. Metal-film  
and carbon composition, axially-leaded resistors can  
also provide good high-frequency performance.  
Copyright © 2008, Texas Instruments Incorporated  
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SBOS444DECEMBER 2008........................................................................................................................................................................................... www.ti.com  
e) Socketing a high-speed part like the OPA4872  
+VCC  
is not recommended. The additional lead length and  
pin-to-pin capacitance introduced by the socket can  
create an extremely troublesome parasitic network  
that can make it almost impossible to achieve a  
smooth, stable frequency response. Best results are  
obtained by soldering the OPA4872 onto the board.  
External  
Pin  
Internal  
Circuitry  
-VCC  
INPUT AND ESD PROTECTION  
Figure 36. Internal ESD Protection  
The OPA4872 is built using a very high-speed  
complementary bipolar process. The internal junction  
breakdown voltages are relatively low for these very  
small geometry devices. These breakdowns are  
reflected in the Absolute Maximum Ratings table. All  
device pins have limited ESD protection using internal  
diodes to the power supplies as shown in Figure 36.  
These diodes provide moderate protection to input  
overdrive voltages above the supplies as well. The  
protection diodes can typically support 30-mA  
continuous current. Where higher currents are  
possible (for example, in systems with ±15-V supply  
parts driving into the OPA4872), current-limiting  
series resistors should be added into the two inputs.  
Keep these resistor values as low as possible  
because high values degrade both noise performance  
and frequency response.  
20  
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PACKAGE MATERIALS INFORMATION  
www.ti.com  
16-Dec-2008  
TAPE AND REEL INFORMATION  
*All dimensions are nominal  
Device  
Package Package Pins  
Type Drawing  
SPQ  
Reel  
Reel  
A0 (mm)  
B0 (mm)  
K0 (mm)  
P1  
W
Pin1  
Diameter Width  
(mm) W1 (mm)  
(mm) (mm) Quadrant  
OPA4872MDREP  
SOIC  
D
14  
2500  
330.0  
16.4  
6.5  
9.0  
2.1  
8.0  
16.0  
Q1  
Pack Materials-Page 1  
PACKAGE MATERIALS INFORMATION  
www.ti.com  
16-Dec-2008  
*All dimensions are nominal  
Device  
Package Type Package Drawing Pins  
SOIC 14  
SPQ  
Length (mm) Width (mm) Height (mm)  
346.0 346.0 33.0  
OPA4872MDREP  
D
2500  
Pack Materials-Page 2  
IMPORTANT NOTICE  
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