AD603ARZ [ADI]

Low Noise, 90 MHz Variable Gain Amplifier; 低噪声, 90 MHz可变增益放大器
AD603ARZ
型号: AD603ARZ
厂家: ADI    ADI
描述:

Low Noise, 90 MHz Variable Gain Amplifier
低噪声, 90 MHz可变增益放大器

模拟IC 信号电路 放大器 光电二极管 PC
文件: 总20页 (文件大小:602K)
中文:  中文翻译
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Low Noise, 90 MHz  
Variable Gain Amplifier  
AD603  
impedance (50 MΩ), low bias (200 nA) differential input; the  
scaling is 25 mV/dB, requiring a gain control voltage of only 1 V  
to span the central 40 dB of the gain range. An overrange and  
underrange of 1 dB is provided whatever the selected range. The  
gain control response time is less than 1 µs for a 40 dB change.  
FEATURES  
Linear-in-dB gain control  
Pin programmable gain ranges  
−11 dB to +31 dB with 90 MHz bandwidth  
9 dB to 51 dB with 9 MHz bandwidth  
Any intermediate range, for example −1 dB to +41 dB  
with 30 MHz bandwidth  
Bandwidth independent of variable gain  
1.3 nV/√Hz input noise spectral density  
0.5 dB typical gain accuracy  
The differential gain control interface allows the use of either  
differential or single-ended positive or negative control voltages.  
Several of these amplifiers may be cascaded and their gain  
control gains offset to optimize the system S/N ratio.  
The AD603 can drive a load impedance as low as 100 Ω with  
low distortion. For a 500 Ω load in shunt with 5 pF, the total  
harmonic distortion for a 1 V sinusoidal output at 10 MHz is  
typically −60 dBc. The peak specified output is 2.5 V  
minimum into a 500 Ω load.  
APPLICATIONS  
RF/IF AGC amplifier  
Video gain control  
A/D range extension  
Signal measurement  
The AD603 uses a patented proprietary circuit topology—the  
X-AMP®. The X-AMP comprises a variable attenuator of 0 dB  
to −42.14 dB followed by a fixed-gain amplifier. Because of the  
attenuator, the amplifier never has to cope with large inputs and  
can use negative feedback to define its (fixed) gain and dynamic  
performance. The attenuator has an input resistance of 100 Ω,  
laser trimmed to 3ꢀ, and comprises a seven-stage R-2R ladder  
network, resulting in an attenuation between tap points of  
6.021 dB. A proprietary interpolation technique provides a  
continuous gain control function which is linear in dB.  
GENERAL DESCRIPTION  
The AD603 is a low noise, voltage-controlled amplifier for use  
in RF and IF AGC systems. It provides accurate, pin selectable  
gains of −11 dB to +31 dB with a bandwidth of 90 MHz or 9 dB  
to 51 dB with a bandwidth of 9 MHz. Any intermediate gain  
range may be arranged using one external resistor. The input  
referred noise spectral density is only 1.3 nV/√Hz and power  
consumption is 125 mW at the recommended 5 V supplies.  
The decibel gain is linear in dB, accurately calibrated, and stable  
over temperature and supply. The gain is controlled at a high  
The AD603 is specified for operation from −40°C to +85°C.  
FUNCTIONAL BLOCK DIAGRAM  
8
6
1
2
VPOS  
VNEG  
GPOS  
GNEG  
SCALING  
REFERENCE  
PRECISION PASSIVE  
INPUT ATTENUATOR  
FIXED-GAIN  
AMPLIFIER  
7
5
V
OUT  
V
G
1
6.44kΩ  
GAIN-  
AD603  
CONTROL  
INTERFACE  
FDBK  
1
694Ω  
0dB  
–6.02dB –12.04dB –18.06dB –24.08dB –30.1dB –36.12dB –42.14dB  
3
4
VINP  
R
R
R
R
R
R
R
1
20Ω  
2R  
2R  
2R  
2R  
2R  
2R  
R
COMM  
R-2R LADDER NETWORK  
1
NOMINAL VALUES.  
Figure 1.  
Rev. G  
Information furnished by Analog Devices is believed to be accurate and reliable.  
However, no responsibility is assumed by Analog Devices for its use, nor for any  
infringements of patents or other rights of third parties that may result from its use.  
Specifications subject to change without notice. No license is granted by implication  
or otherwise under any patent or patent rights of Analog Devices. Trademarks and  
registered trademarks are the property of their respective owners.  
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.  
Tel: 781.329.4700  
Fax: 781.461.3113  
www.analog.com  
© 2005 Analog Devices, Inc. All rights reserved.  
AD603  
TABLE OF CONTENTS  
Specifications..................................................................................... 3  
Using the AD603 in Cascade ........................................................ 14  
Sequential Mode (Optimal S/N Ratio).................................... 14  
Parallel Mode (Simplest Gain Control Interface) .................. 16  
Low Gain Ripple Mode (Minimum Gain Error) ................... 16  
Applications..................................................................................... 18  
A Low Noise AGC Amplifier.................................................... 18  
Caution ........................................................................................ 19  
Outline Dimensions....................................................................... 20  
Ordering Guide .......................................................................... 20  
Absolute Maximum Ratings............................................................ 4  
ESD Caution.................................................................................. 4  
Pin Configuration and Function Descriptions............................. 5  
Typical Performance Characteristics ............................................. 6  
Theory of Operation ...................................................................... 11  
Noise Performance ..................................................................... 11  
The Gain Control Interface....................................................... 12  
Programming the Fixed-Gain Amplifier  
Using Pin Strapping ................................................................... 12  
REVISION HISTORY  
3/05—Rev. F to Rev. G  
Updated Format.................................................................. Universal  
Change to Features ............................................................................1  
Changes to General Description .....................................................1  
Change to Figure 1 ............................................................................1  
Changes to Specifications.................................................................3  
New Figure 4 and Renumbering Subsequent Figures...................6  
Change to Figure 10 ..........................................................................7  
Change to Figure 23 ..........................................................................9  
Change to Figure 29 ........................................................................12  
Updated Outline Dimensions........................................................20  
4/04—Rev. E to Rev. F  
Changes to Specifications.................................................................2  
Changes to Ordering Guide .............................................................3  
8/03—Rev. D to Rev E  
Updated Format.................................................................. Universal  
Changes to Specifications.................................................................2  
Changes to TPCs 2, 3, 4.....................................................................4  
Changes to Sequential Mode (Optimal S/N Ratio) section.........9  
Change to Figure 8 ..........................................................................10  
Updated Outline Dimensions........................................................14  
Rev. G | Page 2 of 20  
AD603  
SPECIFICATIONS  
@ TA = 25°C, VS = 5 V, 500 mV ≤ VG ≤ +500 mV, GNEG = 0 V, 10 dB to +30 dB gain range, RL = 500 Ω, and CL = 5 pF, unless otherwise  
noted.  
Table 1.  
Parameter  
Conditions  
Min  
Typ  
Max  
Unit  
INPUT CHARACTERISTICS  
Input Resistance  
Input Capacitance  
Input Noise Spectral Density1  
Noise Figure  
Pin 3 to Pin 4  
97  
100  
2
1.3  
8.8  
−11  
1.4  
103  
pF  
nV/√Hz  
dB  
dBm  
V
Input short-circuited  
f = 10 MHz, gain = max, RS = 10 Ω  
f = 10 MHz, gain = max, RS = 10 Ω  
1 dB Compression Point  
Peak Input Voltage  
2
OUTPUT CHARACTERISTICS  
−3 dB Bandwidth  
Slew Rate  
Peak Output2  
VOUT = 100 mV rms  
RL ≥ 500 Ω  
RL ≥ 500 Ω  
90  
275  
3.0  
2
MHz  
V/µs  
V
2.5  
Output Impedance  
f ≤ 10 MHz  
Output Short-Circuit Current  
Group Delay Change vs. Gain  
Group Delay Change vs. Frequency  
Differential Gain  
50  
2
2
0.2  
0.2  
−60  
15  
mA  
ns  
ns  
f = 3 MHz; full gain range  
VG = 0 V; f = 1 MHz to 10 MHz  
%
Differential Phase  
Degree  
dBc  
dBm  
Total Harmonic Distortion  
Third Order Intercept  
ACCURACY  
f = 10 MHz, VOUT = 1 V rms  
f = 40 MHz, gain = max, RS = 50 Ω  
Gain Accuracy, f = 100 kHz; Gain (dB) = (40 VG + 10) dB  
TMIN to TMAX  
Gain, f = 10.7 MHz  
−500 mV ≤ VG ≤ +500 mV,  
−1  
0.5  
+1  
dB  
dB  
dB  
dB  
−1.5  
−10.3  
+9.5  
+29.3  
−20  
−30  
−20  
−30  
+1.5  
−8.0  
+11.5  
+31.3  
+20  
+30  
+20  
+30  
VG = -0.5 V  
VG = 0.0 V  
VG = 0.5 V  
VG = 0 V  
−9.0  
+10.5  
+30.3  
dB  
Output Offset Voltage3  
TMIN to TMAX  
Output Offset Variation vs. VG  
TMIN to TMAX  
mV  
mV  
mV  
mV  
−500 mV ≤ VG ≤ +500 mV  
GAIN CONTROL INTERFACE  
Gain Scaling Factor  
TMIN to TMAX  
100 kHz  
39.4  
38  
38.7  
−1.2  
40  
40.6  
42  
39.9  
+2.0  
dB/V  
dB/V  
dB/V  
V
nA  
nA  
10.7 MHz  
39.3  
GNEG, GPOS Voltage Range4  
Input Bias Current  
Input Offset Current  
Differential Input Resistance  
Response Rate  
200  
10  
50  
Pin 1 to Pin 2  
Full 40 dB gain change  
MΩ  
dB/µs  
80  
POWER SUPPLY  
Specified Operating Range  
Quiescent Current  
TMIN to TMAX  
4.75  
6.3  
17  
20  
V
mA  
mA  
12.5  
1 Typical open or short-circuited input; noise is lower when system is set to maximum gain and input is short-circuited. This figure includes the effects of both voltage  
and current noise sources.  
2 Using resistive loads of 500 Ω or greater, or with the addition of a 1 kΩ pull-down resistor when driving lower loads.  
3 The dc gain of the main amplifier in the AD603 is ×35.7; thus, an input offset of 100 µV becomes a 3.57 mV output offset.  
4 GNEG and GPOS, gain control, and voltage range are guaranteed to be within the range of −VS + 4.2 V to +VS − 3.4 V over the full temperature range of −40°C to +85°C.  
Rev. G | Page 3 of 20  
 
 
 
 
 
AD603  
ABSOLUTE MAXIMUM RATINGS  
Table 2.  
Parameter  
Stresses above those listed under Absolute Maximum Ratings  
may cause permanent damage to the device. This is a stress  
rating only; functional operation of the device at these or any  
other conditions above those indicated in the operational  
section of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods may affect  
device reliability.  
Rating  
Supply Voltage VS  
Internal Voltage VINP (Pin 3)  
7.5 V  
2 V Continuous  
VS for 10 ms  
VS  
GPOS, GNEG (Pins 1, 2)  
Internal Power Dissipation1  
Operating Temperature Range  
AD603A  
400 mW  
−40°C to +85°C  
−55°C to +125°C  
−65°C to +150°C  
300°C  
AD603S  
Storage Temperature Range  
Lead Temperature Range (Soldering 60 sec)  
1 Thermal Characteristics:  
8-Lead SOIC Package: θJA = 155°C/W, θJC = 33°C/W,  
8-Lead CERDIP Package: θJA = 140°C/W, θJC = 15°C/W.  
ESD CAUTION  
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on  
the human body and test equipment and can discharge without detection. Although this product features  
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy  
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degrada-  
tion or loss of functionality.  
Rev. G | Page 4 of 20  
 
 
AD603  
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS  
GPOS  
GNEG  
VINP  
1
2
3
4
8
7
6
5
VPOS  
VOUT  
VNEG  
FDBK  
GPOS  
GNEG  
VINP  
1
2
3
4
8
7
6
5
VPOS  
VOUT  
VNEG  
FDBK  
AD603  
AD603  
TOP VIEW  
(Not to Scale)  
TOP VIEW  
(Not to Scale)  
COMM  
COMM  
Figure 2. 8-Lead Plastic SOIC (R) Package  
Figure 3. 8-Lead Ceramic CERDIP (Q) Package  
Table 3. Pin Function Descriptions  
Pin No.  
Mnemonic  
Description  
1
2
3
4
5
6
7
8
GPOS  
GNEG  
VINP  
COMM  
FDBK  
VNEG  
Gain Control Input High (Positive Voltage Increases Gain).  
Gain Control Input Low (Negative Voltage Increases Gain).  
Amplifier Input.  
Amplifier Ground.  
Connection to Feedback Network.  
Negative Supply Input.  
VOUT  
VPOS  
Amplifier Output.  
Positive Supply Input.  
Rev. G | Page 5 of 20  
 
AD603  
TYPICAL PERFORMANCE CHARACTERISTICS  
@ TA = 25°C, VS = 5 V, 500 mV ≤ VG ≤ +500 mV, GNEG = 0 V, 10 dB to +30 dB gain range, RL = 500 Ω, and CL = 5 pF, unless otherwise  
noted.  
40  
30  
20  
10  
0
4
225  
180  
135  
90  
3
2
1
GAIN  
0
45  
–1  
–2  
–3  
–4  
–5  
–6  
0
10.7MHz  
PHASE  
–45  
–90  
–135  
–180  
–225  
100kHz  
–10  
–0.6  
–0.4  
–0.2  
0
0.2  
0.4  
0.6  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
V
(V)  
G
Figure 7. Frequency and Phase Response vs. Gain  
(Gain = +10 dB, PIN = −30 dBm)  
Figure 4. Gain vs. VG at 100 kHz and 10.7 mHz  
4
3
225  
180  
135  
90  
2.5  
2.0  
45MHz  
2
1.5  
1
GAIN  
1.0  
70MHz  
0
45  
10.7MHz  
–1  
–2  
–3  
–4  
–5  
–6  
0
0.5  
PHASE  
–45  
–90  
–135  
–180  
–225  
0
455kHz  
–0.5  
–1.0  
–1.5  
70MHz  
100k  
1M  
10M  
100M  
–0.5 –0.4 –0.3 –0.2 –0.1  
0
0.1  
0.2  
0.3  
0.4  
0.5  
FREQUENCY (Hz)  
GAIN VOLTAGE (Volts)  
Figure 8. Frequency and Phase Response vs. Gain  
(Gain = +30 dB, PIN = −30 dBm)  
Figure 5. Gain Error vs. Gain Control Voltage at 455 kHz,  
10.7 MHz, 45 MHz, 70 MHz  
7.60  
7.40  
7.20  
7.00  
6.80  
6.60  
6.40  
4
3
225  
180  
135  
90  
2
1
GAIN  
0
45  
–1  
–2  
–3  
–4  
–5  
–6  
0
PHASE  
–45  
–90  
–135  
–180  
–225  
–0.6  
–0.4  
–0.2  
0
0.2  
0.4  
0.6  
100k  
1M  
10M  
100M  
GAIN CONTROL VOLTAGE (V)  
FREQUENCY (Hz)  
Figure 9. Group Delay vs. Gain Control Voltage  
Figure 6. Frequency and Phase Response vs. Gain  
(Gain = −10 dB, PIN = −30 dBm)  
Rev. G | Page 6 of 20  
 
 
AD603  
–1.0  
–1.2  
–1.4  
–1.6  
–1.8  
–2.0  
–2.2  
–2.4  
–2.6  
–2.8  
–3.0  
–3.2  
–3.4  
0.1µF  
+5V  
8
HP3326A  
DUAL-  
CHANNEL  
SYNTHESIZER  
3
4
HP3585A  
SPECTRUM  
ANALYZER  
5
7
2
10×  
PROBE  
AD603  
100Ω  
0.1µF  
1
511Ω  
6
–5V  
DATEL  
DVC 8500  
0
50  
100  
200  
500  
1000  
2000  
LOAD RESISTANCE ()  
Figure 10. Third Order Intermodulation Distortion Test Setup  
Figure 13. Typical Output Voltage Swing vs. Load Resistance  
(Negative Output Swing Limits First)  
10dB/DIV  
102  
100  
98  
96  
94  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
Figure 11. Third Order Intermodulation Distortion at 455 kHz  
(10× Probe Used to HP3585A Spectrum Analyzer, Gain = 0 dB, PIN = 0 dBm)  
Figure 14. Input Impedance vs. Frequency (Gain = −10 dB)  
10dB/DIV  
102  
100  
98  
96  
94  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
Figure 12. Third Order Intermodulation Distortion at 10.7 MHz  
(10× Probe Used to HP3585A Spectrum Analyzer, Gain = 0 dB, PIN = 0 dBm)  
Figure 15. Input Impedance vs. Frequency (Gain = +10 dB)  
Rev. G | Page 7 of 20  
AD603  
3V  
102  
INPUT GND  
100MV/DIV  
100  
98  
1V  
OUTPUT GND  
1V/DIV  
96  
94  
–2V  
–49ns  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
50ns  
451ns  
Figure 16. Input Impedance vs. Frequency (Gain = +30 dB)  
Figure 19. Output Stage Overload Recovery Time  
(Input Is 500 ns Period, 50% Duty Cycle Square Wave, Output is Captured  
Using Tektronix 11402 Digitizing Oscilloscope)  
3.5V  
1V  
INPUT  
500mV/DIV  
100  
90  
GND  
500mV  
OUTPUT  
500mV/DIV  
GND  
10  
0%  
200ns  
1V  
–1.5V  
–44ns  
50ns  
456ns  
Figure 17. Gain Control Channel Response Time  
Figure 20. Transient Response, G = 0 dB  
(Input is 500 ns Period, 50% Duty Cycle Square Wave, Output is Captured  
Using Tektronix 11402 Digitizing Oscilloscope)  
4.5V  
3.5V  
INPUT GND  
1V/DIV  
INPUT GND  
100mV/DIV  
500mV  
500mV  
OUTPUT GND  
500mV/DIV  
OUTPUT GND  
500mV/DIV  
–500mV  
–1.5V  
–44ns  
–49ns  
50ns  
451ns  
50ns  
456ns  
Figure 18. Input Stage Overload Recovery Time  
(Input is 500 ns Period, 50% Duty Cycle Square Wave, Output is Captured  
Using Tektronix 11402 Digitizing Oscilloscope)  
Figure 21. Transient Response, G = +20 dB  
(Input is 500 ns Period, 50% Duty Cycle Square Wave, Output is Captured  
Using Tektronix 11402 Digitizing Oscilloscope)  
Rev. G | Page 8 of 20  
AD603  
21  
19  
17  
15  
13  
11  
9
T
R
= 25°C  
= 50  
A
10MHz  
S
0
–10  
–20  
–30  
–40  
–50  
–60  
TEST SETUP FIGURE 23  
20MHz  
7
5
30  
31  
32  
33  
34  
35  
36  
37  
38  
39  
40  
100k  
1M  
10M  
FREQUENCY (Hz)  
100M  
GAIN (dB)  
Figure 25. Noise Figure in 0 dB/40 dB Mode  
Figure 22. PSRR vs. Frequency  
(Worst Case is Negative Supply PSRR, Shown Here)  
0
–5  
T
= 25°C  
A
TEST SETUP FIGURE 23  
0.1  
µF  
+5V  
8
HP3326A  
DUAL-  
CHANNEL  
SYNTHESIZER  
–10  
–15  
–20  
–25  
3
4
HP3585A  
SPECTRUM  
ANALYZER  
5
2
50Ω  
7
AD603  
100  
1
6
0.1  
µ
F
–5V  
DATEL  
DVC 8500  
10  
30  
50  
70  
INPUT FREQUENCY (MHz)  
Figure 23. Test Setup Used for: Noise Figure, Third Order Intercept and  
1 dB Compression Point Measurements  
Figure 26. 1 dB Compression Point, −10 dB/+30 dB Mode, Gain = +30 dB  
23  
20  
T
R
= 25°C  
= 50V  
A
T
= 25°C  
A
S
TEST SETUP FIGURE 23  
21  
19  
17  
15  
13  
11  
9
70MHz  
TEST SETUP FIGURE 23  
18  
16  
14  
12  
10  
0
30MHz  
50MHz  
40MHz  
30MHz  
10MHz  
70MHz  
7
5
20  
21  
22  
23  
24  
25  
26  
27  
28  
29  
30  
–20  
–10  
INPUT LEVEL (dBm)  
0
GAIN (dB)  
Figure 24. Noise Figure in −10 dB/+30 dB Mode  
Figure 27. Third Order Intercept −10 dB/+30 dB Mode, Gain = +10 dB  
Rev. G | Page 9 of 20  
AD603  
20  
18  
16  
14  
12  
10  
T
= 25°C  
= 50Ω  
A
R
R
R
S
= 50Ω  
IN  
= 100Ω  
L
TEST SETUP FIGURE 23  
30MHz  
40MHz  
70MHz  
8
–40  
–30  
INPUT LEVEL (dBm)  
–20  
Figure 28. Third Order Intercept −10 dB/+30 dB Mode, Gain = +30 dB  
Rev. G | Page 10 of 20  
AD603  
THEORY OF OPERATION  
continuous attenuation from 0 dB to 42.14 dB. It will help in  
The AD603 comprises a fixed-gain amplifier, preceded by a  
broadband passive attenuator of 0 dB to 42.14 dB, having a gain  
control scaling factor of 40 dB per volt. The fixed gain is laser-  
trimmed in two ranges, to either 31.07 dB (×35.8) or 50 dB  
(×358), or may be set to any range in between using one  
external resistor between Pin 5 and Pin 7. Somewhat higher  
gain can be obtained by connecting the resistor from Pin 5 to  
common, but the increase in output offset voltage limits the  
maximum gain to about 60 dB. For any given range, the  
bandwidth is independent of the voltage-controlled gain. This  
system provides an underrange and overrange of 1.07 dB in all  
cases; for example, the overall gain is −11.07 dB to +31.07 dB in  
the maximum bandwidth mode (Pin 5 and Pin 7 strapped).  
understanding the AD603 to think in terms of a mechanical  
means for moving this slider from left to right; in fact, its  
position is controlled by the voltage between Pin 1 and Pin 2.  
The details of the gain control interface are discussed later.  
The gain is at all times very exactly determined, and a linear-in-  
dB relationship is automatically guaranteed by the exponential  
nature of the attenuation in the ladder network (the X-AMP  
principle). In practice, the gain deviates slightly from the ideal  
law, by about 0.2 dB peak (see, for example, Figure 5).  
NOISE PERFORMANCE  
An important advantage of the X-AMP is its superior noise  
performance. The nominal resistance seen at inner tap points is  
41.7 Ω (one third of 125 Ω), which exhibits a Johnson noise  
spectral density (NSD) of 0.83 nV/√Hz (that is, √4kTR) at 27°C,  
which is a large fraction of the total input noise. The first stage  
of the amplifier contributes a further 1 nV/√Hz, for a total input  
noise of 1.3 nV/√Hz. It will be apparent that it is essential to use  
a low resistance in the ladder network to achieve the very low  
specified noise level. The signal’s source impedance forms a  
voltage divider with the AD603s 100 Ω input resistance. In  
some applications, the resulting attenuation may be  
This X-AMP structure has many advantages over former  
methods of gain control based on nonlinear elements. Most  
importantly, the fixed-gain amplifier can use negative feedback  
to increase its accuracy. Since large inputs are first attenuated,  
the amplifier input is always small. For example, to deliver a  
1 V output in the −1 dB/+41 dB mode (that is, using a fixed  
amplifier gain of 41.07 dB) its input is only 8.84 mV; thus the  
distortion can be very low. Equally important, the small-signal  
gain and phase response, and thus the pulse response, are  
essentially independent of gain.  
unacceptable, requiring the use of an external buffer or  
preamplifier to match a high impedance source to the low  
impedance AD603.  
Figure 29 is a simplified schematic. The input attenuator is a  
seven-section R-2R ladder network, using untrimmed resistors  
of nominally R = 62.5 Ω, which results in a characteristic  
resistance of 125 Ω 20ꢀ. A shunt resistor is included at the  
input and laser trimmed to establish a more exact input  
resistance of 100 Ω 3ꢀ, which ensures accurate operation  
(gain and HP corner frequency) when used in conjunction with  
external resistors or capacitors.  
The noise at maximum gain (that is, at the 0 dB tap) depends on  
whether the input is short-circuited or open-circuited: when  
shorted, the minimum NSD of slightly over 1 nV/√Hz is  
achieved; when open, the resistance of 100 Ω looking into the  
first tap generates 1.29 nV/√Hz, so the noise increases to a total  
of 1.63 nV/√Hz. (This last calculation would be important if the  
AD603 were preceded by, for example, a 900 Ω resistor to allow  
operation from inputs up to 10 V rms.) As the selected tap  
moves away from the input, the dependence of the noise on  
source impedance quickly diminishes.  
The nominal maximum signal at input VINP is 1 V rms ( 1.4 V  
peak) when using the recommended 5 V supplies, although  
operation to 2 V peak is permissible with some increase in HF  
distortion and feedthrough. Pin 4 (COMM) must be connected  
directly to the input ground; significant impedance in this  
connection will reduce the gain accuracy.  
Apart from the small variations just discussed, the signal-to-  
noise (S/N) ratio at the output is essentially independent of the  
attenuator setting. For example, on the −11 dB/+31 dB range,  
the fixed gain of ×35.8 raises the output NSD to 46.5 nV/√Hz.  
Thus, for the maximum undistorted output of 1 V rms and a  
1 MHz bandwidth, the output S/N ratio would be 86.6 dB, that  
is, 20 log (1 V/46.5 µV).  
The signal applied at the input of the ladder network is  
attenuated by 6.02 dB by each section; thus, the attenuation to  
each of the taps is progressively 0 dB, 6.02 dB, 12.04 dB,  
18.06 dB, 24.08 dB, 30.1 dB, 36.12 dB, and 42.14 dB. A unique  
circuit technique is employed to interpolate between these tap  
points, indicated by the slider in Figure 29, thus providing  
Rev. G | Page 11 of 20  
 
AD603  
8
6
1
2
VPOS  
VNEG  
GPOS  
GNEG  
SCALING  
REFERENCE  
PRECISION PASSIVE  
INPUT ATTENUATOR  
FIXED-GAIN  
AMPLIFIER  
7
5
V
OUT  
V
G
1
6.44kΩ  
GAIN-  
AD603  
CONTROL  
INTERFACE  
FDBK  
1
694Ω  
0dB  
–6.02dB –12.04dB –18.06dB –24.08dB –30.1dB –36.12dB –42.14dB  
3
4
VINP  
R
R
R
R
R
R
R
1
20Ω  
2R  
2R  
2R  
2R  
2R  
2R  
R
COMM  
R-2R LADDER NETWORK  
1
NOMINAL VALUES.  
Figure 29. Simplified Block Diagram  
For example, if the gain is to be controlled by a DAC providing  
a positive only ground-referenced output, the Gain Control Low  
(GNEG) pin should be biased to a fixed offset of 500 mV to set  
the gain to −10 dB when Gain Control High (GPOS) is at zero,  
and to 30 dB when at 1.00 V.  
THE GAIN CONTROL INTERFACE  
The attenuation is controlled through a differential, high  
impedance (50 MΩ) input, with a scaling factor which is laser-  
trimmed to 40 dB per volt, that is, 25 mV/dB. An internal band  
gap reference ensures stability of the scaling with respect to  
supply and temperature variations.  
It is a simple matter to include a voltage divider to achieve other  
scaling factors. When using an 8-bit DAC having an FS output  
of 2.55 V (10 mV/bit), a divider ratio of 2 (generating 5 mV/bit)  
would result in a gain-setting resolution of 0.2 dB/bit. The use  
of such offsets is valuable when two AD603s are cascaded, when  
various options exist for optimizing the S/N profile, as will be  
shown later.  
When the differential input voltage VG = 0 V, the attenuator  
slider is centered, providing an attenuation of 21.07 dB. For the  
maximum bandwidth range, this results in an overall gain of  
10 dB (= −21.07 dB + 31.07 dB). When the control input is  
−500 mV, the gain is lowered by 20 dB (= 0.500 V × 40 dB/V) to  
−10 dB; when set to +500 mV, the gain is increased by 20 dB to  
30 dB. When this interface is overdriven in either direction, the  
gain approaches either −11.07 dB (= − 42.14 dB + 31.07 dB) or  
31.07 dB (= 0 + 31.07 dB), respectively. The only constraint on  
the gain control voltage is that it be kept within the common-  
mode range (−1.2 V to +2.0 V assuming +5 V supplies) of the  
gain control interface.  
PROGRAMMING THE FIXED-GAIN AMPLIFIER  
USING PIN STRAPPING  
Access to the feedback network is provided at Pin 5 (FDBK).  
The user may program the gain of the AD603s output amplifier  
using this pin, as shown in Figure 30, Figure 31, and Figure 32.  
There are three modes: in the default mode, FDBK is  
unconnected, providing the range +9 dB/+51 dB; when VOUT  
and FDBK are shorted, the gain is lowered to −11 dB/+31 dB;  
and when an external resistor is placed between VOUT and FDBK  
any intermediate gain can be achieved, for example, −1 dB/+41  
dB. Figure 33 shows the nominal maximum gain vs. external  
resistor for this mode.  
The basic gain of the AD603 can thus be calculated using the  
following simple expression:  
Gain (dB) = 40 VG +10  
(1)  
where VG is in volts. When Pin 5 and Pin 7 are strapped (see  
next section), the gain becomes  
Gain (dB) = 40 VG + 20 for 0 to +40 dB  
1
2
3
4
8
7
6
5
and  
VC1  
VC2  
GPOS VPOS  
AD603  
VPOS  
VNEG  
Gain (dB) = 40 VG + 30 for +10 to +50 dB  
(2)  
GNEG VOUT  
VOUT  
The high impedance gain control input ensures minimal  
loading when driving many amplifiers in multiple channel or  
cascaded applications. The differential capability provides  
flexibility in choosing the appropriate signal levels and  
polarities for various control schemes.  
VIN  
VINP  
VNEG  
COMM FDBK  
Figure 30. −10 dB to +30 dB; 90 MHz Bandwidth  
Rev. G | Page 12 of 20  
 
 
AD603  
1
2
3
4
8
7
6
5
Optionally, when a resistor is placed from FDBK to COMM,  
VC1  
VC2  
GPOS VPOS  
VPOS  
VNEG  
AD603  
GNEG VOUT  
higher gains can be achieved. This fourth mode is of limited  
value because of the low bandwidth and the elevated output  
offsets; it is thus not included in Figure 30, Figure 31, or  
Figure 32.  
VOUT  
VIN  
VINP  
VNEG  
2.15k  
COMM FDBK  
The gain of this amplifier in the first two modes is set by the  
ratio of on-chip laser-trimmed resistors. While the ratio of these  
resistors is very accurate, the absolute value of these resistors  
can vary by as much as 20ꢀ. Thus, when an external resistor is  
connected in parallel with the nominal 6.44 kΩ 20ꢀ internal  
resistor, the overall gain accuracy is somewhat poorer. The  
worst-case error occurs at about 2 kΩ (see Figure 34).  
5.6pF  
Figure 31. 0 dB to 40 dB; 30 MHz Bandwidth  
1
2
3
4
8
7
6
5
VC1  
VC2  
GPOS VPOS  
VPOS  
AD603  
GNEG VOUT  
VOUT  
1.2  
VIN  
VINP  
VNEG  
VNEG  
18pF  
–1:VdB (OUT) – (–1):VdB (O  
)
REF  
1.0  
0.8  
COMM FDBK  
0.6  
0.4  
Figure 32. 10 dB to 50 db; 9 MHz to Set Gain  
0.2  
0
–0.2  
–0.4  
–0.6  
–0.8  
–1.0  
52  
50  
48  
46  
44  
42  
40  
38  
36  
34  
32  
30  
–1:VdB (OUT)  
VdB (OUT) – VdB (O  
)
REF  
10  
100  
1k  
10k  
100k  
1M  
VdB (OUT)  
R
()  
EXT  
–2:VdB (OUT)  
Figure 34. Worst-Case Gain Error, Assuming Internal Resistors have a  
Maximum Tolerance of −20% (Top Curve) or =20% (Bottom Curve)  
While the gain bandwidth product of the fixed-gain amplifier is  
about 4 GHz, the actual bandwidth is not exactly related to the  
maximum gain. This is because there is a slight enhancing of  
the ac response magnitude on the maximum bandwidth range,  
due to higher order poles in the open-loop gain function; this  
mild peaking is not present on the higher gain ranges. Figure 30,  
Figure 31, and Figure 32 show how an optional capacitor may  
be added to extend the frequency response in high gain modes.  
10  
100  
1k  
10k  
100k  
1M  
R
()  
EXT  
Figure 33. Gain vs. REXT, Showing Worst-Case Limits Assuming Internal  
Resistors have a Maximum Tolerance of 20%  
Rev. G | Page 13 of 20  
 
 
 
AD603  
USING THE AD603 IN CASCADE  
be provided by resistive dividers operating from a common  
voltage reference.  
Two or more AD603s can be connected in series to achieve  
higher gain. Invariably, ac coupling must be used to prevent the  
dc offset voltage at the output of each amplifier from  
overloading the following amplifier at maximum gain. The  
required high-pass coupling network will usually be just a  
capacitor, chosen to set the desired corner frequency in  
conjunction with the well-defined 100 Ω input resistance of the  
following amplifier.  
90  
85  
80  
75  
70  
65  
60  
55  
50  
For two AD603s, the total gain control range becomes 84 dB  
(2 × 42.14 dB); the overall −3 dB bandwidth of cascaded stages  
will be somewhat reduced. Depending on the pin strapping, the  
gain and bandwidth for two cascaded amplifiers can range from  
−22 dB to +62 dB (with a bandwidth of about 70 MHz) to  
+22 dB to +102 dB (with a bandwidth of about 6 MHz).  
–0.2  
0.2  
0.6  
1.0  
(V)  
1.4  
1.8  
2.2  
V
C
There are several ways of connecting the gain control inputs in  
cascaded operation. The choice depends on whether it is  
important to achieve the highest possible instantaneous signal-  
to-noise ratio (ISNR), or, alternatively, to minimize the ripple in  
the gain error. The following examples feature the AD603  
programmed for maximum bandwidth; the explanations apply  
to other gain/bandwidth combinations with appropriate  
changes to the arrangements for setting the maximum gain.  
Figure 35. SNR vs. Control Voltage–Sequential Control (1 MHz Bandwidth)  
The gains are offset (Figure 39) such that A2s gain is increased  
only after A1s gain has reached its maximum value. Note that  
for a differential input of –600 mV or less, the gain of a single  
amplifier (A1 or A2) will be at its minimum value of −11.07 dB;  
for a differential input of +600 mV or more, the gain will be at  
its maximum value of 31.07 dB. Control inputs beyond these  
limits will not affect the gain and can be tolerated without  
damage or foldover in the response. This is an important aspect  
of the AD603s gain control response. (See the Specifications  
section for more details on the allowable voltage range.) The  
gain is now  
SEQUENTIAL MODE (OPTIMAL S/N RATIO)  
In the sequential mode of operation, the ISNR is maintained at  
its highest level for as much of the gain control range as  
possible. Figure 35 shows the SNR over a gain range of −22 dB  
to +62 dB, assuming an output of 1 V rms and a 1 MHz  
bandwidth; Figure 36, Figure 37, and Figure 38 show the general  
connections to accomplish this. Here, both the positive gain  
control inputs (GPOS) are driven in parallel by a positive-only,  
ground-referenced source with a range of 0 V to +2 V, while the  
negative gain control inputs (GNEG) are biased by stable  
voltages to provide the needed gain offsets. These voltages may  
Gain (dB) = 40 VG + GO  
(3)  
where VG is the applied control voltage and GO is determined by  
the gain range chosen. In the explanatory notes that follow, it is  
assumed the maximum bandwidth connections are used, for  
which GO is −20 dB.  
A1  
A2  
–40.00dB  
–51.07dB  
–8.93dB  
–42.14dB  
GPOS GNEG  
–42.14dB  
INPUT  
0dB  
31.07dB  
31.07dB  
OUTPUT  
–20dB  
GPOS  
GNEG  
V
V
G2  
G1  
V
= 0.473V  
V
= 1.526V  
O2  
O1  
V
= 0V  
C
Figure 36. AD603 Gain Control Input Calculations for Sequential Control Operation VC = 0 V  
0dB  
–11.07dB  
31.07dB  
0dB  
–42.14dB  
GPOS GNEG  
INPUT  
0dB  
31.07dB  
31.07dB  
OUTPUT  
20dB  
GPOS  
GNEG  
V
V
G2  
G1  
V
= 0.473V  
V
= 1.526V  
O1  
O2  
V
= 1.0V  
C
Figure 37. AD603 Gain Control Calculations for Sequential Control Operation VC = 1.0 V  
Rev. G | Page 14 of 20  
 
 
 
 
AD603  
0dB  
–28.93dB  
31.07dB  
0dB  
–2.14dB  
GPOS GNEG  
INPUT  
0dB  
31.07dB  
31.07dB  
OUTPUT  
60dB  
GPOS  
GNEG  
V
V
G2  
G1  
V
= 0.473V  
V
= 1.526V  
O1  
O2  
V
= 2.0V  
C
Figure 38. AD603 Gain Control Input Calculations for Sequential Operation VC = 2.0 V  
70  
60  
+31.07dB  
+10dB  
+31.07dB  
+28.96dB  
COMBINED  
1
50  
40  
A1  
A2  
1
–11.07dB  
–8.93dB  
A1  
–11.07dB  
30  
0.473  
1.526  
20  
GAIN  
(dB) –22.14 –20  
0
0.5  
0
1.0  
20  
1.50  
40  
2.0  
60  
V
62.14  
(V)  
C
10  
0
A2  
1
GAIN OFFSET OF 1.07dB, OR 26.75mV.  
–10  
–20  
–30  
Figure 39. Explanation of Offset Calibration for Sequential Control  
With reference to Figure 36, Figure 37, and Figure 38, note that  
–0.2  
0.2  
0.6  
1.0  
1.4  
1.8  
2.0  
V
G1 refers to the differential gain control input to A1, and VG2  
refers to the differential gain control input to A2. When VG is 0,  
G1 = −473 mV and thus the gain of A1 is −8.93 dB (recall that  
V
C
Figure 40. Plot of Separate and Overall Gains in Sequential Control  
V
90  
the gain of each individual amplifier in the maximum  
bandwidth mode is –10 dB for VG = −500 mV and 10 dB for VG  
= 0 V); meanwhile, VG2 = −1.908 V so the gain of A2 is pinned at  
−11.07 dB. The overall gain is thus –20 dB. See Figure 36.  
80  
70  
60  
50  
40  
30  
20  
10  
When VG = +1.00 V, VG1 = 1.00 V − 0.473 V = +0.526 V, which  
sets the gain of A1 to at nearly its maximum value of 31.07 dB,  
while VG2 = 1.00 V − 1.526 V = 0.526 V, which sets A2s gain at  
nearly its minimum value of −11.07 dB. Close analysis shows  
that the degree to which neither AD603 is completely pushed to  
its maximum nor minimum gain exactly cancels in the overall  
gain, which is now +20 dB. See Figure 37.  
–0.2  
0.2  
0.6  
1.0  
1.4  
1.8  
2.0  
When VG = 2.0 V, the gain of A1 is pinned at 31.07 dB and that  
of A2 is near its maximum value of 28.93 dB, resulting in an  
overall gain of 60 dB (see Figure 38). This mode of operation is  
further clarified by Figure 40, which is a plot of the separate  
gains of A1 and A2 and the overall gain vs. the control voltage.  
Figure 41 is a plot of the SNR of the cascaded amplifiers vs. the  
control voltage. Figure 42 is a plot of the gain error of the  
cascaded stages vs. the control voltages.  
V
C
Figure 41. SNR for Cascaded Stages—Sequential Control  
Rev. G | Page 15 of 20  
 
 
 
AD603  
2.0  
90  
85  
80  
75  
70  
65  
60  
55  
50  
1.5  
1.0  
0.5  
0
–0.5  
–1.0  
–1.5  
–2.0  
–0.2  
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2  
–0.2  
0
0.2  
0.4  
0.6  
0.8  
1.0  
1.2  
V
V
C
C
Figure 42. Gain Error for Cascaded Stages–Sequential Control  
Figure 44. ISNR for Cascaded Stages—Parallel Control  
PARALLEL MODE (SIMPLEST GAIN CONTROL  
INTERFACE)  
LOW GAIN RIPPLE MODE (MINIMUM GAIN ERROR)  
As can be seen in Figure 42 and Figure 43, the error in the gain  
is periodic, that is, it shows a small ripple. (Note that there is  
also a variation in the output offset voltage, which is due to the  
gain interpolation, but this is not exact in amplitude.) By  
offsetting the gains of A1 and A2 by half the period of the  
ripple, that is, by 3 dB, the residual gain errors of the two  
amplifiers can be made to cancel. Figure 45 shows much lower  
gain ripple when configured in this manner. Figure 46 plots the  
ISNR as a function of gain; it is very similar to that in the  
parallel mode.  
In this mode, the gain control of voltage is applied to both  
inputs in parallel—the GPOS pins of both A1 and A2 are  
connected to the control voltage and the GNEW inputs are  
grounded. The gain scaling is then doubled to 80 dB/V,  
requiring only a 1.00 V change for an 80 dB change of gain:  
Gain = (dB) = 80 VG + GO  
(4)  
where, as before, GO depends on the range selected; for example,  
in the maximum bandwidth mode, GO is +20 dB. Alternatively,  
the GNEG pins may be connected to an offset voltage of  
0.500 V, in which case GO is −20 dB.  
3.0  
2.5  
2.0  
The amplitude of the gain ripple in this case is also doubled, as  
shown in Figure 43, while the instantaneous signal-to-noise  
ratio at the output of A2 now decreases linearly as the gain  
increases, as shown in Figure 44.  
1.5  
1.0  
0.5  
0
–0.5  
–1.0  
–1.5  
–2.0  
–2.5  
–3.0  
2.0  
1.5  
1.0  
0.5  
–0.1  
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1  
0
V
C
–0.5  
–1.0  
–1.5  
–2.0  
Figure 45. Gain Error for Cascaded Stages—Low Ripple Mode  
–0.2  
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2  
V
C
Figure 43. Gain Error for Cascaded Stages—Parallel Control  
Rev. G | Page 16 of 20  
 
 
 
 
 
AD603  
90  
85  
80  
75  
70  
65  
60  
55  
50  
–0.2  
0
0.2  
0.4  
0.6  
0.8  
1.0  
1.2  
V
C
Figure 46. ISNR vs. Control Voltage—Low Ripple Mode  
Rev. G | Page 17 of 20  
AD603  
APPLICATIONS  
The circuit operates as follows. A1 and A2 are cascaded.  
Capacitor C1 and the 100 Ω of resistance at the input of A1  
form a time constant of 10 µs. C2 blocks the small dc offset  
voltage at the output of A1 (which might otherwise saturate A2  
at its maximum gain) and introduces a high-pass corner at  
about 16 kHz, eliminating low frequency noise.  
A LOW NOISE AGC AMPLIFIER  
Figure 47 shows the ease with which the AD603 can be  
connected as an AGC amplifier. The circuit illustrates many of  
the points previously discussed: It uses few parts, has linear-in-  
dB gain, operates from a single supply, uses two cascaded  
amplifiers in sequential gain mode for maximum S/N ratio, and  
an external resistor programs each amplifiers gain. It also uses a  
simple temperature-compensated detector.  
A half-wave detector is used, based on Q1 and R8. The current  
into capacitor CAV is just the difference between the collector  
current of Q2 (biased to be 300 µA at 300 K, 27°C) and the  
collector current of Q1, which increases with the amplitude of  
the output signal.  
The circuit operates from a single 10 V supply. Resistors R1, R2,  
R3, and R4 bias the common pins of A1 and A2 at 5 V. This pin  
is a low impedance point and must have a low impedance path  
to ground, provided here by the 100 µF tantalum capacitors and  
the 0.1 µF ceramic capacitors.  
The automatic gain control voltage, VAGC, is the time integral of  
this error current. In order for VAGC (and thus the gain) to  
remain insensitive to short-term amplitude fluctuations in the  
output signal, the rectified current in Q1 must, on average,  
exactly balance the current in Q2. If the output of A2 is too  
small to do this, VAGC will increase, causing the gain to increase,  
until Q1 conducts sufficiently.  
The cascaded amplifiers operate in sequential gain. Here, the  
offset voltage between the Pin 2 (GNEG) of A1 and A2 is 1.05 V  
(42.14 dB × 25 mV/dB), provided by a voltage divider  
consisting of resistors R5, R6, and R7. Using standard values, the  
offset is not exact, but it is not critical for this application.  
Consider the case where R8 is zero and the output voltage VOUT  
is a square wave at, say, 455 kHz, which is well above the corner  
frequency of the control loop.  
The gain of both A1 and A2 is programmed by resistors R13  
and R14, respectively, to be about 42 dB; thus the maximum  
gain of the circuit is twice that, or 84 dB. The gain control range  
can be shifted up by as much as 20 dB by appropriate choices of  
R13 and R14.  
10V  
C11  
0.1µF  
R9  
1.54kΩ  
R10  
1.24kΩ  
THIS CAPACITOR SETS  
AGC TIME CONSTANT  
C7  
0.1µF  
Q2  
2N3906  
V
AGC  
10V  
C8  
R11  
3.83kΩ  
5V  
0.1µF  
R13  
2.49kΩ  
10V  
8
C1  
0.1µF  
C
0.1µF  
AV  
8
Q1  
2N3904  
R14  
2.49kΩ  
C2  
0.1µF  
6
3
4
J1  
C9  
0.1µF  
1
5
2
R12  
4.99kΩ  
RT  
A1  
R8  
806Ω  
10V  
6
7
3
4
100Ω  
AD603  
5
2
A2  
AD603  
10V  
7
J2  
R1  
2.49kΩ  
1
C10  
0.1µF  
R3  
2.49kΩ  
2
+
1
C3  
100µF  
C4  
0.1µF  
R2  
2.49kΩ  
2
+
C5  
100µF  
C6  
0.1µF  
R4  
2.49kΩ  
AGC LINE  
1V OFFSET FOR  
SEQUENTIAL GAIN  
R5  
5.49kΩ  
R7  
3.48kΩ  
10V  
R6  
1.05kΩ  
5.5V  
6.5V  
1
2
RT PROVIDES A 50INPUT IMPEDANCE.  
C3 AND C5 ARE TANTALUM.  
Figure 47. A Low Noise AGC Amplifier  
Rev. G | Page 18 of 20  
 
 
AD603  
During the time VOUT is negative with respect to the base  
voltage of Q1, Q1 conducts; when VOUT is positive, it is cut off.  
Since the average collector current of Q1 is forced to be 300 µA,  
and the square wave has a duty cycle of 1:1, Q1s collector  
current when conducting must be 600 µA. With R8 omitted, the  
peak amplitude of VOUT is forced to be just the VBE of Q1 at  
600 µA, typically about 700 mV, or 2 VBE peak-to-peak. This  
voltage, the amplitude at which the output stabilizes, has a  
strong negative temperature coefficient (TC), typically  
−1.7 mV/°C. Although this may not be troublesome in some  
applications, the correct value of R8 will render the output  
stable with temperature.  
inexpensive 2N3904/2N3906 pair and sine wave signals, the  
recommended value is 806 Ω.  
This resistor also serves to lower the peak current in Q1 when  
more typical signals (usually sinusoidal) are involved, and the  
1.8 kHz LP filter it forms with CAV helps to minimize distortion  
due to ripple in VAGC. Note that the output amplitude under sine  
wave conditions will be higher than for a square wave, since the  
average value of the current for an ideal rectifier would be 0.637  
times as large, causing the output amplitude to be 1.88  
(= 1.2/0.637) V, or 1.33 V rms. In practice, the somewhat  
nonideal rectifier results in the sine wave output being regulated  
to about 1.4 V rms, or 3.6 V p-p.  
To understand this, note that the current in Q2 is made to be  
proportional to absolute temperature (PTAT). For the moment,  
continue to assume that the signal is a square wave.  
The bandwidth of the circuit exceeds 40 MHz. At 10.7 MHz, the  
AGC threshold is 100 µV (−67 dBm) and its maximum gain is  
83 dB (20 log 1.4 V/100 µV). The circuit holds its output at  
1.4 V rms for inputs as low as −67 dBm to +15 dBm (82 dB),  
where the input signal exceeds the AD603s maximum input  
rating. For a 30 dBm input at 10.7 MHz, the second harmonic is  
34 dB down from the fundamental and the third harmonic is  
35 dB down.  
When Q1 is conducting, VOUT is now the sum of VBE and a  
voltage that is PTAT and that can be chosen to have an equal  
but opposite TC to that of the VBE. This is actually nothing more  
than an application of the band gap voltage reference principle.  
When R8 is chosen such that the sum of the voltage across it  
and the VBE of Q1 is close to the band gap voltage of about 1.2 V,  
VOUT will be stable over a wide range of temperatures, provided,  
of course, that Q1 and Q2 share the same thermal environment.  
CAUTION  
Careful component selection, circuit layout, power supply  
decoupling, and shielding are needed to minimize the AD603s  
susceptibility to interference from signals such as those from  
radio and TV stations. In bench evaluation, it is recommended  
to place all of the components into a shielded box and using  
feedthrough decoupling networks for the supply voltage. Circuit  
layout and construction are also critical, since stray capacitances  
and lead inductances can form resonant circuits and are a  
potential source of circuit peaking, oscillation, or both.  
Since the average emitter current is 600 µA during each half  
cycle of the square wave, a resistor of 833 Ω would add a PTAT  
voltage of 500 mV at 300 K, increasing by 1.66 mV/°C. In  
practice, the optimum value will depend on the type of  
transistor used and, to a lesser extent, on the waveform for  
which the temperature stability is to be optimized; for the  
Rev. G | Page 19 of 20  
 
AD603  
OUTLINE DIMENSIONS  
0.005 (0.13) 0.055 (1.40)  
MIN  
MAX  
8
5
5.00 (0.1968)  
4.80 (0.1890)  
0.310 (7.87)  
0.220 (5.59)  
8
1
5
4
1
4
6.20 (0.2440)  
5.80 (0.2284)  
4.00 (0.1574)  
3.80 (0.1497)  
PIN 1  
0.100 (2.54) BSC  
0.405 (10.29) MAX  
0.320 (8.13)  
0.290 (7.37)  
1.27 (0.0500)  
BSC  
0.50 (0.0196)  
0.25 (0.0099)  
0.060 (1.52)  
0.015 (0.38)  
× 45°  
1.75 (0.0688)  
1.35 (0.0532)  
0.200 (5.08)  
MAX  
0.25 (0.0098)  
0.10 (0.0040)  
0.150 (3.81)  
MIN  
0.200 (5.08)  
0.125 (3.18)  
8°  
0.51 (0.0201)  
0.31 (0.0122)  
0° 1.27 (0.0500)  
COPLANARITY  
0.10  
0.25 (0.0098)  
0.17 (0.0067)  
0.015 (0.38)  
0.008 (0.20)  
0.023 (0.58)  
0.014 (0.36)  
SEATING  
PLANE  
SEATING  
PLANE  
15°  
0°  
0.40 (0.0157)  
0.070 (1.78)  
0.030 (0.76)  
COMPLIANT TO JEDEC STANDARDS MS-012-AA  
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS  
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR  
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.  
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS  
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR  
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN  
Figure 48. 8-Lead Ceramic Dual In-Line Package [CERDIP]  
(Q-8)  
Figure 49. 8-Lead Standard Small Outline Package [SOIC-N]  
Narrow Body  
(R-8)  
Dimensions shown in inches and (millimeters)  
Dimensions shown in millimeters and (inches)  
ORDERING GUIDE  
Part Number  
AD603AR  
AD603AR-REEL  
AD603AR-REEL7  
AD603ARZ1  
AD603ARZ-REEL1  
AD603ARZ-REEL71  
AD603AQ  
Temperature Range  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
−40°C to +85°C  
−55°C to +125°C  
Package Description  
Package Option  
8-Lead SOIC  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
Q-8  
Q-8  
8-Lead SOIC, 13" Reel  
8-Lead SOIC, 7" Reel  
8-Lead SOIC  
8-Lead SOIC, 13" Reel  
8-Lead SOIC, 7" Reel  
8-Lead CERDIP  
8-Lead CERDIP  
Evaluation Board  
DIE  
AD603SQ/883B2  
AD603-EB  
AD603ACHIPS  
1 Z = Pb-free part.  
2 Refer to AD603 Military data sheet. Also available as 5962-9457203MPA.  
©
2005 Analog Devices, Inc. All rights reserved. Trademarks and  
registered trademarks are the property of their respective owners.  
C00539–0–3/05(G)  
Rev. G | Page 20 of 20  
 
 
 
 

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