OP777AR [ADI]
Precision Micropower Single Supply Operational Amplifier; 精密微功耗单电源运算放大器
| 型号： | OP777AR |
| 厂家： | 
ADI |
| 描述： | Precision Micropower Single Supply Operational Amplifier |
| 文件： | 总12页 (文件大小：163K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Precision Micropower
Single Supply
Operational Amplifier
a
OP777
FUNCTIONAL BLOCK DIAGRAMS
8-Lead MSOP
FEATURES
Low Offset Voltage: 100 ꢂV Max
Low Input Bias Current: 10 nA Max
Single-Supply Operation: 2.7 V to 30 V
Dual-Supply Operation: ꢃ1.35 V to ꢃ15 V
Low Supply Current: 270 ꢂA/Amp
Unity Gain Stable
(RM Suffix)
NC
ꢀIN
ꢁIN
Vꢀ
1
8
NC
V+
OUT
NC
OP777
4
5
NC = NO CONNECT
No Phase Reversal
8-Lead SOIC
(R Suffix)
APPLICATIONS
Precision Current Measurement
Line or Battery-Powered Instrumentation
Remote Sensors
NC
NC
V+
1
2
3
4
8
7
6
5
ꢀIN
+IN
Vꢀ
OP777
Precision Filters
OUT
NC
NC = NO CONNECT
GENERAL DESCRIPTION
The OP777 is a precision single supply amplifier featuring
micropower operation and rail-to-rail output ranges. This ampli-
fier provides improved performance over the industry-standard
OP07 with 15 V supplies and offers the further advantage of
true single supply operation down to 2.7 V, and smaller package
footprint than any other high-voltage precision bipolar amplifier.
Outputs are stable with capacitive loads of over 1000 pF. Supply
current is less than 300 µA per amplifier at 5 V. 500 Ω series resis-
tors protect the inputs, allowing input signal levels to exceed either
power supply rail by up to 3 V without causing phase reversal of the
output signal or causing damage to the amplifier. The proprietary
fabrication process yields a very low-voltage noise corner frequency
under 10 Hz, greatly improving the low-frequency noise perfor-
mance of the OP07 and similar amplifiers. The specially fabricated
input PNP transistors operate with very low input bias currents while
allowing operation with large differential voltages, eliminating a
common limitation of many precision amplifiers and enabling
application of the OP777 in precision comparator and rectifier
circuits. This large differential voltage capability also further reduces
the need for external protection devices such as clamping diodes.
Applications for these amplifiers include both line powered and
portable instrumentation, remote sensor signal conditioning, and
precision filters.
The OP777 is specified over the extended industrial (–40°C to
+85°C) temperature range and is available in 8-lead MSOP and
8-lead SOIC packages. The OP777 uses a standard operational
amplifier pinout, allowing for easy drop-in replacement of lower
performance amplifiers in most circuits. Surface mount devices
in MSOP packages are available in tape and reel only.
REV. 0
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 2000
OP777–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS (VS = 5.0 V, VCM = 2.5 V, TA = 25ꢄC unless otherwise noted)
Parameter
Symbol
Conditions
Min
Typ Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
VOS
100
200
11
2
4
µV
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
µV
Input Bias Current
Input Offset Current
Input Voltage Range
IB
IOS
nA
nA
V
0
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
CMRR
AVO
∆VOS/∆T
VCM = 0 V to 4 V
RL = 10 kΩ , VO = 0.5 V to 4.5 V
–40°C ≤ TA ≤ +85°C
104
300
110
500
0.3
dB
V/mV
µV/°C
1.3
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
VOH
VOL
IOUT
IL = 1 mA, –40°C ≤ TA ≤ +85°C
IL = 1 mA, –40°C ≤ TA ≤ +85°C
VDROPOUT < 1 V
4.88
120
V
mV
mA
140
Short Circuit Limit
10
POWER SUPPLY
Power Supply Rejection Ratio
Supply Current/Amplifier
PSRR
ISY
VS = 3 V to 30 V
VO = 0 V
–40°C ≤ TA ≤ +85°C
130
270
dB
µA
µA
270
320
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
SR
GBP
RL = 2 kΩ
0.2
0.7
V/µs
MHz
NOISE PERFORMANCE
Voltage Noise
Voltage Noise Density
Current Noise Density
enp-p
en
in
0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
0.4
15
0.13
µVp-p
nV/√Hz
pA/√Hz
Specifications subject to change without notice.
–2–
REV. 0
OP777
ELECTRICAL CHARACTERISTICS (VS = ꢃ15.0 V, VCM = 0 V, TA = 25ꢄC unless otherwise noted)
Parameter
Symbol
Conditions
Min
Typ Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
VOS
100
200
10
2
+14
µV
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
µV
Input Bias Current
Input Offset Current
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
IB
IOS
nA
nA
V
dB
V/mV
µV/°C
–15
110
1,000 2,500
0.3
CMRR
AVO
∆VOS/∆T
V
CM = –15 V to +14 V
120
RL = 10 kΩ , VO = –14.5 V to +14.5 V
–40°C ≤ TA ≤ +85°C
1.3
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
VOH
VOL
IOUT
IL = 1 mA, –40°C ≤ TA ≤ +85°C
IL = 1 mA, –40°C ≤ TA ≤ +85°C
14.9
V
V
mA
–14.9
Short Circuit Limit
30
POWER SUPPLY
Power Supply Rejection Ratio
Supply Current/Amplifier
PSRR
ISY
VS = 1.5 V to 15 V
VO = 0 V
–40°C ≤ TA ≤ +85°C
120
130
350
dB
µA
µA
350
400
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
SR
GBP
RL = 2 kΩ
0.2
0.7
V/µs
MHz
NOISE PERFORMANCE
Voltage Noise
Voltage Noise Density
enp-p
en
in
0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
0.4
15
0.13
µVp-p
nV/√Hz
pA/√Hz
Current Noise Density
Specifications subject to change without notice.
REV. 0
–3–
OP777
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . VS– – 3 V to VS+ + 3 V
1
Package Type
ꢅJA
ꢅJC
Unit
8-Lead MSOP (RM)
8-Lead SOIC (R)
190
158
44
43
°C/W
°C/W
Differential Input Voltage . . . . . . . . . . . . . .
Supply Voltage
Output Short-Circuit Duration to GND . . . . . . . . . Indefinite
Storage Temperature Range
R, RM Packages . . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Operating Temperature Range
NOTE
1θJA is specified for worst-case conditions, i.e., θJA is specified for device soldered
in circuit board for surface-mount packages.
OP777 . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Junction Temperature Range
R, RM Packages . . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec) . . . . . . . . 300°C
ESD (HBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 kV
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi-
tions for extended periods may affect device reliability.
ORDERING GUIDE
Temperature
Range
Package
Description
Package
Option
Branding
Information
Model
OP777ARM
OP777AR
–40°C to +85°C
–40°C to +85°C
8-Lead MSOP
8-Lead SOIC
RM-8
SO-8
A1A
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
the OP777 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recom-
mended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
–4–
REV. 0
Typical Performance Characteristics–
OP777
30
220
220
V
V
T
= ꢃ15V
= 0V
= ꢀ40ꢄC TO +85ꢄC
A
V
V
T
= 5V
= 2.5V
= 25ꢄC
V
V
T
= ꢃ15V
= 0V
= 25ꢄC
SY
SY
SY
200
180
160
200
180
160
CM
CM
CM
25
20
15
10
5
A
A
140
120
100
80
140
120
100
80
60
60
40
40
20
0
20
0
0
0
0.2
0.4
0.6
0.8
1.0
1.2
ꢀ100
0
20 40 60 80 100
ꢀ100
0
20 40 60 80 100
ꢀ80ꢀ60 ꢀ40ꢀ20
ꢀ80ꢀ60 ꢀ40ꢀ20
INPUT OFFSET DRIFT – ꢂV/ꢄC
OFFSET VOLTAGE – ꢂV
OFFSET VOLTAGE – ꢂV
Figure 3. Input Offset Voltage Drift
Distribution
Figure 1. Input Offset Voltage
Distribution
Figure 2. Input Offset Voltage
Distribution
10k
30
25
20
15
10
5
10k
1k
V
T
= ꢃ15V
= 25ꢄC
V
T
= 5V
= 25ꢄC
S
S
V
V
= ꢃ15V
= 0V
= 25ꢄC
SY
A
A
CM
1k
T
A
SINK
100
10
100
10
SOURCE
SINK
1.0
1.0
SOURCE
0.1
0
0.1
0
0
0.001
0.01
0.1
1
10
100
0.001
0.01
0.1
1
10
100
3
5
7
4
6
8
LOAD CURRENT – mA
INPUT BIAS CURRENT – nA
LOAD CURRENT – mA
Figure 6. Output Voltage to Supply
Rail vs. Load Current
Figure 4. Input Bias Current
Distribution
Figure 5. Output Voltage to Supply
Rail vs. Load Current
350
10
5
500
V
= ꢃ15V
T
= 25ꢄC
SY
A
I
(V = ꢃ15V)
400
200
100
0
SY+ SY
300
250
200
150
100
50
0
I
(V = 5V)
SY+ SY
ꢀ5
ꢀ10
ꢀ15
ꢀ20
ꢀ25
ꢀ30
ꢀ100
ꢀ200
ꢀ300
ꢀ400
ꢀ500
I
(V = 5V)
SYꢀ SY
I
(V = ꢃ15V)
SYꢀ SY
0
0
5
10
15
20
25
30
35
ꢀ60ꢀ40 ꢀ20
0
20 40 60 80 100 120 140
ꢀ60ꢀ40 ꢀ20
0
20 40 60 80 100 120 140
SUPPLY VOLTAGE – V
TEMPERATURE – ꢄC
TEMPERATURE – ꢄC
Figure 9. Supply Current vs.
Supply Voltage
Figure 7. Input Bias Current vs.
Temperature
Figure 8. Supply Current vs.
Temperature
REV. 0
–5–
OP777
60
50
70
60
50
70
60
50
40
30
20
10
0
V
C
R
= 5V
V = ꢃ15V
SY
V
C
R
= ꢃ15V
SY
SY
= 0
C
= 0
= 0
=
LOAD
LOAD
LOAD
LOAD
=
R
= 2kꢇ
LOAD
LOAD
40
0
0
A
= ꢀ100
V
30
45
40
30
45
20
90
90
A
= ꢀ10
V
10
135
180
225
270
20
10
135
180
225
270
0
A
= +1
V
ꢀ10
ꢀ20
ꢀ30
ꢀ40
0
ꢀ10
ꢀ10
ꢀ20
ꢀ30
ꢀ20
ꢀ30
100
1k
10k
100k
1M
10M
100M
1k
10k
100k
1M
10M 100M
10
100 1k
10k 100k 1M 10M 100M
FREQUENCY – Hz
FREQUENCY – Hz
FREQUENCY – Hz
Figure 11. Open Loop Gain and
Phase Shift vs. Frequency
Figure 12. Closed Loop Gain vs.
Frequency
Figure 10. Open Loop Gain and
Phase Shift vs. Frequency
300
270
240
210
180
150
120
90
300
270
240
210
180
150
120
90
60
V
= 5V
V
C
R
= 5V
V
= ꢃ15V
SY
SY
SY
50
40
= 0
= 2kꢇ
A = 1
V
LOAD
LOAD
A
= ꢀ100
V
30
A
= 1
V
20
A
= ꢀ10
V
10
0
A
= +1
V
ꢀ10
ꢀ20
ꢀ30
ꢀ40
A
= 100
100k
V
60
A
= 10
60
A
= 10
V
A
= 100
1k
V
V
30
30
0
0
100
1k
10k
1M
10M 100M
100
10k
100k
1M
10M 100M
1k
10k
100k
1M
10M
100M
FREQUENCY – Hz
FREQUENCY – Hz
FREQUENCY – Hz
Figure 14. Output Impedance vs.
Frequency
Figure 15. Output Impedance vs.
Frequency
Figure 13. Closed Loop Gain vs.
Frequency
V
R
C
= ꢃ15V
= 2kꢇ
= 300pF
V
C
R
= ꢃ2.5V
= 300pF
= 2kꢇ
V
R
C
= ꢃ2.5V
= 2kꢇ
= 300pF
SY
SY
SY
L
L
L
L
L
L
V
= 100mV
IN
TIME – 100ꢂs/DIV
TIME – 10ꢂs/DIV
TIME – 100ꢂs/DIV
Figure 17. Large Signal Transient
Response
Figure 18. Small Signal Transient
Response
Figure 16. Large Signal Transient
Response
–6–
REV. 0
OP777
40
35
30
25
20
15
10
5
35
30
25
20
V
= ꢃ2.5V
= 2kꢇ
= 100mV
V
= ꢃ15V
= 2kꢇ
L
= 100mV
V
= ꢃ15V
= 300pF
= 2kꢇ
SY
SY
SY
R
V
R
V
C
R
V
L
L
L
IN
IN
= 100mV
IN
+OS
ꢀOS
15
10
5
0
0
1
10
100
1k
1
10
100
1k
10k
TIME – 10ꢂs/DIV
CAPACITANCE – pF
CAPACITANCE – pF
Figure 19. Small Signal Transient
Response
Figure 20. Small Signal Overshoot
vs. Load Capacitance
Figure 21. Small Signal Overshoot
vs. Load Capacitance
V
A
= ꢃ15V
= 1
S
INPUT
INPUT
V
+200mV
INPUT
0V
0V
OUTPUT
V
R
A
= ꢃ15V
= 10kꢇ
= ꢀ100
V
R
A
= ꢃ2.5V
= 10kꢇ
= ꢀ100
SY
SY
ꢀ200mV
L
L
V
V
V
= 200mV
V
= 200mV
IN
IN
+2V
0V
0V
ꢀ2V
OUTPUT
OUTPUT
TIME – 400ꢂs/DIV
TIME – 40ꢂs/DIV
TIME – 40ꢂs/DIV
Figure 22. Positive Overvoltage
Recovery
Figure 23. Negative Overvoltage
Recovery
Figure 24. No Phase Reversal
140
140
140
120
100
80
V
= ꢃ2.5V
V
= ꢃ15V
SY
SY
V
= ꢃ2.5V
SY
120
100
80
60
40
20
0
120
100
80
60
40
20
0
+PSRR
ꢀPSRR
60
40
20
0
10
100
1k
10k 100k
1M
10M
10
100
1k
10k 100k
1M
10M
10
100
1k
10k 100k
1M
10M
FREQUENCY – Hz
FREQUENCY – Hz
FREQUENCY – Hz
Figure 25. CMRR vs. Frequency
Figure 26. CMRR vs. Frequency
Figure 27. PSRR vs. Frequency
REV. 0
–7–
OP777
140
120
100
80
V
= ꢃ15V
V
= 5V
V
= ꢃ15V
SY
SY
GAIN = 10M
SY
GAIN = 10M
+PSRR
ꢀPSRR
60
40
20
0
10
100
1k
10k 100k
1M
10M
TIME – 1s/DIV
TIME – 1s/DIV
FREQUENCY – Hz
Figure 28. PSRR vs. Frequency
Figure 29. 0.1 Hz to 10 Hz Input
Voltage Noise
Figure 30. 0.1 Hz to 10 Hz Input
Voltage Noise
90
90
80
70
90
V
= ꢃ2.5V
V
= ꢃ15V
SY
V
= ꢃ15V
SY
SY
80
70
80
70
60
50
40
30
20
10
60
50
40
30
20
10
60
50
40
30
20
10
0
100
200
300
400
500
0
100
200
300
400
500
0
50
100
150
200
250
FREQUENCY – Hz
FREQUENCY – Hz
FREQUENCY – Hz
Figure 31. Voltage Noise Density
Figure 32. Voltage Noise Density
Figure 33. Voltage Noise Density
50
50
40
V = 5V
SY
V
= ꢃ15V
V
= ꢃ2.5V
SY
SY
40
40
35
30
30
20
30
20
I
SCꢀ
I
SCꢀ
25
20
15
10
5
10
0
10
0
ꢀ10
ꢀ10
ꢀ20
ꢀ30
ꢀ20
ꢀ30
I
SC+
I
SC+
ꢀ40
ꢀ50
ꢀ40
ꢀ50
0
0
500
1k
1.5k
2.0k
2.5k
ꢀ60ꢀ40 ꢀ20
0
20 40 60 80 100 120 140
ꢀ60ꢀ40 ꢀ20
0
20 40 60 80 100 120 140
FREQUENCY – Hz
TEMPERATURE – ꢄC
TEMPERATURE – ꢄC
Figure 35. Short Circuit Current vs.
Temperature
Figure 36. Short Circuit Current vs.
Temperature
Figure 34. Voltage Noise Density
–8–
REV. 0
OP777
160
150
140
130
120
110
100
4.95
4.94
4.93
4.92
4.91
4.90
4.89
14.964
14.962
14.960
V
= 5V
= 1mA
V
= 5V
SY
SY
I = 1mA
L
V
= ꢃ15V
SY
I = 1mA
L
I
L
14.958
14.956
14.954
14.952
14.950
14.948
90
80
70
14.946
14.944
ꢀ40 ꢀ20
ꢀ40 ꢀ20
0
ꢀ60
0
20 40 60 80 100 120 140
ꢀ60
20 40 60 80 100 120 140
TEMPERATURE – ꢄC
ꢀ40 ꢀ20
ꢀ60
0
20 40 60 80 100 120 140
TEMPERATURE – ꢄC
TEMPERATURE – ꢄC
Figure 37. Output Voltage High vs.
Temperature
Figure 38. Output Voltage Low vs.
Temperature
Figure 39. Output Voltage High vs.
Temperature
1.5
ꢀ14.930
V
= ꢃ15V
SY
= 1mA
V
V
= ꢃ15V
= 0V
= 25ꢄC
SY
I
L
CM
1.0
0.5
0
ꢀ14.935
ꢀ14.940
ꢀ14.945
T
A
ꢀ0.5
ꢀ1.0
ꢀ1.5
ꢀ14.950
ꢀ14.955
ꢀ14.960
ꢀ40 ꢀ20
0
ꢀ60
20 40 60 80 100 120 140
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TIME – Minutes
TEMPERATURE – ꢄC
Figure 41. Warm-Up Drift
Figure 40. Output Voltage Low vs.
Temperature
REV. 0
–9–
OP777
BASIC OPERATION
100kꢇ
The OP777 amplifier uses a precision Bipolar PNP input stage
coupled with a high-voltage CMOS output stage. This enables
this amplifier to feature an input voltage range which includes the
negative supply voltage (often ground-in single-supply applications)
and also swing to within 1 mV of the output rails. Additionally, the
input voltage range extends to within 1 V of the positive supply rail.
The epitaxial PNP input structure provides high breakdown voltage,
high gain, and input bias current figure comparable to that obtained
with “Darlington” input stage amplifier but without the drawbacks
(i.e., severe penalties for input voltage range, offset, drift and noise).
PNP input structure also greatly lowers the noise and reduces the dc
input error terms.
100kꢇ
+3V
ꢀ0.27V
100kꢇ
OP777
100kꢇ
ꢀ0.1V
V
= 1kHz at 400mV p-p
IN
Figure 43. OP777 Configured as a Difference Amplifier
Operating at VCM < 0 V
Input Over Voltage Protection
When the input of an amplifier is more than a diode drop below
Supply Voltage
The amplifiers are fully specified with a single 5 V supply and, due
to design and process innovations, can also operate with a supply
voltage from 2.7 V up to 30 V. This allows operation from most
split supplies used in current industry practice, with the advantage
of substantially increased input and output voltage ranges over
conventional split-supply amplifiers. The OP777 series is specified
with (VSY = 5 V, V– = 0 V and VCM = 2.5 V which is most suitable
for single supply application. With PSRR of 130 dB (0.3 µV/V) and
CMRR of 110 dB (3 µV/V) offset is minimally affected by power
supply or common-mode voltages. Dual supply, 15 V operation
is also fully specified.
V
EE, large currents will flow from the substrate (V– pin) to the
input pins which can destroy the device. In the case of OP777,
differential voltage equal to the supply voltage will not cause any
problem (see Figure 44). OP777 has built in 500 Ω internal current
limiting resistors, in series with the inputs, to minimize the chances
of damage. It is a good practice to keep the current flowing into the
inputs below 5 mA. In this context it should also be noted that the
high breakdown of the input transistors removes the necessity for
clamp diodes between the inputs of the amplifier; a feature that is
mandatory on many precision op amps. Unfortunately, such
clamp diodes greatly interfere with many application circuits such
as precision rectifiers and comparators. The OP777 series is free
from such limitations.
Input Common-Mode Voltage Range
The OP777 is rated with an input common-mode voltage which
extends from minus supply to 1 V of the Positive supply. However,
the amplifier can still operate with input voltages slightly below
VEE. In Figure 43, OP777 is configured as a difference amplifier
with a single supply of 2.7 V and negative dc common-mode volt-
ages applied at the inputs terminals. A 400 mV p-p input is then
applied to the noninverting input. It can be seen from the graph
below that the output does not show any distortion. Micropower
operation is maintained by using large input and feedback resistors.
30V
OP777
V p-p = 32 V
Figure 44a. Unity Gain Follower
V
= ꢃ15V
SY
V
OUT
V
IN
0V
V
OUT
V
IN
TIME – 0.2ms/DIV
Figure 42. Input and Output Signals with VCM < 0 V
TIME – 400ꢂs/DIV
Figure 44b. Input Voltage Can Exceed the Supply Voltage
Without Damage
–10–
REV. 0
OP777
Phase Reversal
Output Short Circuit
Many amplifiers misbehave when one or both of the inputs are
forced beyond the input common-mode voltage range. Phase
reversal is typified by the transfer function of the amplifier, effectively
reversing its transfer polarity. In some cases this can cause lockup in
servo systems and may cause permanent damage or nonrecoverable
parameter shifts to the amplifier. Many amplifiers feature compensa-
tion circuitry to combat these effects, but some are only effective for
the inverting input. Additionally, many of these schemes only work
for a few hundred millivolts or so beyond the supply rails. OP777
has a protection circuit against phase reversal when one or both
inputs are forced beyond their input common voltage range. It
is not recommended that the parts be continuously driven more
than 3 V beyond the rails.
The output of the OP777 series amplifier is protected from damage
against accidental shorts to either supply voltage, provided that the
maximum die temperature is not exceeded on a long-term basis (see
Absolute Maximum Rating section). Current of up to 30 mA does
not cause any damage.
A Low-Side Current Monitor
In the design of power supply control circuits, a great deal of design
effort is focused on ensuring a pass transistor’s long-term reliability
over a wide range of load current conditions. As a result, monitoring
and limiting device power dissipation is of prime importance in
these designs. Figure 48 shows an example of 5 V, single supply
current monitor that can be incorporated into the design of a voltage
regulator with foldback current limiting or a high current power
supply with crowbar protection. The design capitalizes on the
OP777’s common-mode range that extends to ground. Current
is monitored in the power supply return where a 0.1 Ω shunt
resistor, RSENSE, creates a very small voltage drop. The voltage at the
inverting terminal becomes equal to the voltage at the noninverting
terminal through the feedback of Q1, which is a 2N2222 or equiva-
lent NPN transistor. This makes the voltage drop across R1 equal to
the voltage drop across RSENSE. Therefore, the current through Q1
becomes directly proportional to the current through RSENSE, and
the output voltage is given by:
V
= ꢃ15V
SY
V
IN
V
OUT
R2
R1
VOUT = 5V −
× RSENSE × I
L
TIME – 400ꢂs/DIV
The voltage drop across R2 increases with IL increasing, so VOUT
decreases with higher supply current being sensed. For the element
values shown, the VOUT transfer characteristic is –2.5 V/A, decreas-
,
Figure 45. No Phase Reversal
Output Stage
The CMOS output stage has excellent (and fairly symmetric) output
drive and with light loads can actually swing to within 1 mV of both
supply rails. This is considerably better than similar amplifiers
featuring (so-called) rail-to-rail bipolar output stages. OP777 is
stable in the voltage follower configuration and responds to signals
as low as 1 mv above ground in single supply operation.
ing from VEE
.
5V
2.49kꢇ
V
OUT
Q1
5V
2.7V TO 30V
100ꢇ
OP777
V
= 1mV
0.1ꢇ
OUT
RETURN TO
GROUND
V
= 1mV
IN
OP777
R
SENSE
Figure 48. A Low-Side Load Current Monitor
Figure 46. Follower Circuit
1.0mV
TIME – 10ꢂs/DIV
Figure 47. Rail-to-Rail Operation
REV. 0
–11–
OP777
The OP777 can be very useful in many single supply bridge applica-
tions. Figure 49 shows a single supply bridge circuit in which
its output is linearly proportional to the fractional deviation (ꢀ)
of the bridge. Note that ꢀ = ∆R/R.
A single supply current source is shown in Figure 51. Large resistors
are used to maintain micropower operation. Output current can be
adjusted by changing the R2B resistor. Compliance voltage is:
VL ≤ VSAT − VS
= 300
AR1ꢉV
REF
15V
V
=
ꢈ + 2.5V
O
2R2
ꢆR1
R1
10pF
2
ꢈ =
2.7V TO 30V
OP777
6
RG = 10kꢇ
100kꢇ
REF
192
2
100kꢇ
10.1kꢇ
1Mꢇ
2.5V
0.1ꢂF
OP777
4
3
1Mꢇ
R1 = 100kꢇ
REF
192
R2B
15V
2.7kꢇ
15V
10pF
4
3
I
O
R1(1+ꢈ)
V1
10.1kꢇ
R1
R2 = R2A + R2B
R2
R1 ꢉ R2B
= 1mA ꢀ 11mA
+
R2A
97.3kꢇ
V
O
OP777
V
R
LOAD
L
I
=
V
S
O
R1(1+ꢈ)
OP777
R1
ꢀ
R2
V2
Figure 51. Single Supply Current Source
Figure 49. Linear Response Bridge, Single Supply
A single supply instrumentation amplifier using two OP777 ampli-
fiers is shown in Figure 52.
In systems, where dual supplies are available, circuit of Figure 50
could be used to detect bridge outputs that are linearly related to
fractional deviation of the bridge.
15V
10.1kꢇ
R2 = 1Mꢇ
2.7V TO 30V
2.7V TO 30V
1kꢇ
1Mꢇ
REF
192
2N2222
R1 = 10.1kꢇ
OP777
V
O
R2
12kꢇ
OP777
V1
V2
OP777
3
4
20kꢇ
+15V
R1
R1
R
V
= 100 (V2 ꢀ V1)
O
0.02mV V1 ꢀ V2 290mV
V
O
R(1+ꢈ)
2mV
V
29V
+15V
OP777
OUT
USE MATCHED RESISTORS
ꢀ15V
R2
R1
ꢆR
R
V
=
V
ꢈ
O
REF
Figure 52. Single Supply Micropower Instrumentation
Amplifier
OP777
ꢈ =
ꢀ15V
Figure 50. Linear Response Bridge
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead ꢂSOIC
(RM Suffix)
8-Lead SOIC
(R Suffix)
0.122 (3.10)
0.114 (2.90)
0.1968 (5.00)
0.1890 (4.80)
8
1
5
4
8
5
4
0.1574 (4.00)
0.1497 (3.80)
0.2440 (6.20)
0.2284 (5.80)
0.122 (3.10)
0.114 (2.90)
0.199 (5.05)
0.187 (4.75)
1
PIN 1
0.0688 (1.75)
0.0532 (1.35)
0.0196 (0.50)
0.0099 (0.25)
x 45°
0.0098 (0.25)
0.0040 (0.10)
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.120 (3.05)
0.112 (2.84)
8°
0°
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.043 (1.09)
0.037 (0.94)
SEATING
PLANE
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
0.006 (0.15)
0.002 (0.05)
33ꢄ
0.018 (0.46)
0.008 (0.20)
27ꢄ
0.028 (0.71)
0.016 (0.41)
0.011 (0.28)
0.003 (0.08)
SEATING
PLANE
–12–
REV. 0
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