AD OP777ARM

a
FEATURES
Low Offset Voltage: 100 V Max
Low Input Bias Current: 10 nA Max
Single-Supply Operation: 2.7 V to 30 V
Dual-Supply Operation: 1.35 V to 15 V
Low Supply Current: 270 A/Amp
Unity Gain Stable
No Phase Reversal
APPLICATIONS
Precision Current Measurement
Line or Battery-Powered Instrumentation
Remote Sensors
Precision Filters
Precision Micropower
Single Supply
Operational Amplifier
OP777
FUNCTIONAL BLOCK DIAGRAMS
8-Lead MSOP
(RM Suffix)
NC
IN
IN
V
1
8
NC
V+
OUT
NC
OP777
4
5
NC = NO CONNECT
8-Lead SOIC
(R Suffix)
NC 1
IN 2
+IN 3
V 4
8 NC
OP777
7 V+
6 OUT
5 NC
NC = NO CONNECT
GENERAL DESCRIPTION
The OP777 is a precision single supply amplifier featuring
micropower operation and rail-to-rail output ranges. This amplifier 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 resistors 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 performance 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
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
OP777–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS (V = 5.0 V, V
S
Parameter
Symbol
INPUT CHARACTERISTICS
Offset Voltage
VOS
CM
= 2.5 V, TA = 25C unless otherwise noted)
Conditions
Min
IB
IOS
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
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
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Short Circuit Limit
VOH
VOL
IOUT
IL = 1 mA, –40°C ≤ TA ≤ +85°C
IL = 1 mA, –40°C ≤ TA ≤ +85°C
VDROPOUT < 1 V
4.88
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
120
Input Bias Current
Input Offset Current
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
0
104
300
Typ
110
500
0.3
Max
Unit
100
200
11
2
4
µV
µV
nA
nA
V
dB
V/mV
µV/°C
1.3
140
V
mV
mA
270
320
dB
µA
µA
± 10
130
270
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 (V = 15.0 V, V
S
Parameter
Symbol
INPUT CHARACTERISTICS
Offset Voltage
VOS
CM
= 0 V, TA = 25C unless otherwise noted)
Conditions
Min
IB
IOS
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
–40°C ≤ TA ≤ +85°C
CMRR
AVO
∆VOS /∆T
VCM = –15 V to +14 V
RL = 10 kΩ , VO = –14.5 V to +14.5 V
–40°C ≤ TA ≤ +85°C
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Short Circuit Limit
VOH
VOL
IOUT
IL = 1 mA, –40°C ≤ TA ≤ +85°C
IL = 1 mA, –40°C ≤ TA ≤ +85°C
14.9
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
Input Bias Current
Input Offset Current
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Offset Voltage Drift
–15
110
1,000
Typ
Max
Unit
100
200
10
2
+14
µV
µV
nA
nA
V
dB
V/mV
µV/°C
120
2,500
0.3
1.3
–14.9
± 30
130
350
350
400
V
V
mA
dB
µA
µA
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.
REV. 0
–3–
OP777
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . VS– – 3 V to VS+ + 3 V
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
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
Package Type
JA1
JC
Unit
8-Lead MSOP (RM)
8-Lead SOIC (R)
190
158
44
43
°C/W
°C/W
NOTE
1
θJA is specified for worst-case conditions, i.e., θJA is specified for device soldered
in circuit board for surface-mount packages.
*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 listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ORDERING GUIDE
Model
Temperature
Range
Package
Description
Package
Option
Branding
Information
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 recommended to avoid performance degradation or loss of functionality.
–4–
WARNING!
ESD SENSITIVE DEVICE
REV. 0
Typical Performance Characteristics–OP777
160
140
120
100
80
60
140
120
100
80
60
20
0
100 8060 4020 0 20 40 60 80 100
OFFSET VOLTAGE – V
0
100 8060 4020 0 20 40 60 80 100
OFFSET VOLTAGE – V
Figure 2. Input Offset Voltage
Distribution
15
10
5
0
1k
SINK
100
SOURCE
10
1.0
3
5
7
4
6
INPUT BIAS CURRENT – nA
0
0.001
8
Figure 4. Input Bias Current
Distribution
0.01
0.1
1
10
LOAD CURRENT – mA
400
0
5
10
15
20
SUPPLY CURRENT – A
5
200
100
ISY+ (VSY = 5V)
0
100
200
ISY (VSY = 5V)
300
400
30
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
500
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
REV. 0
10
SINK
1.0
SOURCE
0.01
0.1
1
10
LOAD CURRENT – mA
100
350
TA = 25C
ISY+ (VSY = 15V)
25
Figure 7. Input Bias Current vs.
Temperature
100
Figure 6. Output Voltage to Supply
Rail vs. Load Current
500
VSY = 15V
VS = 15V
TA = 25C
0
0.001
100
Figure 5. Output Voltage to Supply
Rail vs. Load Current
10
1.2
0.1
0.1
0
0.2
0.4
0.6
0.8
1.0
INPUT OFFSET DRIFT – V/C
Figure 3. Input Offset Voltage Drift
Distribution
OUTPUT VOLTAGE – mV
20
10
0
VS = 5V
TA = 25C
1k
OUTPUT VOLTAGE – mV
25
15
10k
10k
VSY = 15V
VCM = 0V
TA = 25C
20
5
40
20
30
NUMBER OF AMPLIFIERS
160
40
Figure 1. Input Offset Voltage
Distribution
INPUT BIAS CURRENT – nA
180
VSY = 15V
VCM = 0V
TA = 40C TO +85C
25
ISY (VSY = 15V)
Figure 8. Supply Current vs.
Temperature
–5–
300
SUPPLY CURRENT – A
NUMBER OF AMPLIFIERS
180
VSY = 5V
VCM = 2.5V
TA = 25C
200
NUMBER OF AMPLIFIERS
200
30
220
VSY = 15V
VCM = 0V
TA = 25C
NUMBER OF AMPLIFIERS
220
250
200
150
100
50
0
0
5
10
15
20
25
SUPPLY VOLTAGE – V
30
Figure 9. Supply Current vs.
Supply Voltage
35
OP777
0
40
45
30
90
20
135
10
180
0
225
10
270
50
45
30
90
20
135
10
180
0
225
10
270
20
30
30
100
100
1k
10k 100k 1M
FREQUENCY – Hz
10M 100M
AV = 100
30
AV = 10
0
10
AV = +1
20
30
40
1k
10M
10k
100k
1M
10M
FREQUENCY – Hz
Figure 13. Closed Loop Gain vs.
Frequency
150
120
90
AV = 100
AV = 10
1k
100k
10k
1M
FREQUENCY – Hz
10M
AV = +1
20
10k
100M
100k
1M
10M
FREQUENCY – Hz
VSY = 15V
240
210
AV = 1
180
150
120
90
60
AV = 100 AV = 10
0
100
100M
TIME – 100s/DIV
Figure 17. Large Signal Transient
Response
–6–
1k
10k
1M
100k
FREQUENCY – Hz
10M
100M
Figure 15. Output Impedance vs.
Frequency
VSY = 15V
RL = 2k
CL = 300pF
VOLTAGE – 1V/DIV
Figure 16. Large Signal Transient
Response
10
30
Figure 14. Output Impedance vs.
Frequency
VSY = 2.5V
RL = 2k
CL = 300pF
TIME – 100s/DIV
0
270
180
0
100
AV = 10
300
AV = 1
210
100M
10
Figure 12. Closed Loop Gain vs.
Frequency
VSY = 5V
240
60
20
40
1k
100M
30
VOLTAGE – 1V/DIV
CLOSED-LOOP GAIN – dB
40
10
10k
1M
100k
FREQUENCY – Hz
270
OUTPUT IMPEDANCE – VSY = 5V
CLOAD = 0
RLOAD = 2k
50
20
1k
300
60
AV = 100
30
30
Figure 11. Open Loop Gain and
Phase Shift vs. Frequency
Figure 10. Open Loop Gain and
Phase Shift vs. Frequency
40
VOLTAGE – 50mV/DIV
10
0
40
20
VSY = 15V
CLOAD = 0
RLOAD = 2k
50
PHASE SHIFT – Degrees
60
OUTPUT IMPEDANCE – OPEN-LOOP GAIN – dB
50
60
VSY = 5V
CLOAD = 0
RLOAD =
CLOSED-LOOP GAIN – dB
60
70
OPEN-LOOP GAIN – dB
VSY = 15V
CLOAD = 0
RLOAD =
PHASE SHIFT – Degrees
70
VSY = 2.5V
CL = 300pF
RL = 2k
VIN = 100mV
TIME – 10s/DIV
Figure 18. Small Signal Transient
Response
REV. 0
OP777
40
30
25
20
15
10
5
0
100
10
CAPACITANCE – pF
1
TIME – 10s/DIV
Figure 19. Small Signal Transient
Response
35
VSY = 2.5V
RL = 2k
VIN = 100mV
35
SMALL SIGNAL OVERSHOOT – %
SMALL SIGNAL OVERSHOOT – %
VOLTAGE – 50mV/DIV
VSY = 15V
CL = 300pF
RL = 2k
VIN = 100mV
25
+OS
20
OS
15
10
5
0
1k
Figure 20. Small Signal Overshoot
vs. Load Capacitance
VSY = 15V
RL = 2k
VIN = 100mV
30
1k
10
100
CAPACITANCE – pF
1
10k
Figure 21. Small Signal Overshoot
vs. Load Capacitance
VS = 15V
AV = 1
INPUT
INPUT
+200mV
VSY = 15V
RL = 10k
AV = 100
VIN = 200mV
VSY = 2.5V
RL = 10k
AV = 100
VIN = 200mV
200mV
+2V
0V
2V
VOLTAGE – 5V/DIV
INPUT
0V
0V
OUTPUT
0V
OUTPUT
OUTPUT
TIME – 40s/DIV
TIME – 400s/DIV
TIME – 40s/DIV
Figure 22. Positive Overvoltage
Recovery
Figure 23. Negative Overvoltage
Recovery
140
140
VSY = 2.5V
Figure 24. No Phase Reversal
140
VSY = 15V
VSY = 2.5V
120
120
120
100
100
100
80
60
PSRR – dB
CMRR – dB
CMRR – dB
+PSRR
80
60
PSRR
80
60
40
40
40
20
20
20
0
10
100
10k 100k
1k
FREQUENCY – Hz
1M
Figure 25. CMRR vs. Frequency
REV. 0
10M
0
10
100
10k 100k
1k
FREQUENCY – Hz
1M
10M
Figure 26. CMRR vs. Frequency
–7–
0
10
100
10k 100k
1k
FREQUENCY – Hz
1M
Figure 27. PSRR vs. Frequency
10M
OP777
140
VSY = 15V
+PSRR
80
PSRR
60
40
VOLTAGE – 1V/DIV
VOLTAGE – 1V/DIV
100
PSRR – dB
VSY = 15V
GAIN = 10M
VSY = 5V
GAIN = 10M
120
20
10
100
10k 100k
1k
FREQUENCY – Hz
1M
10M
Figure 28. PSRR vs. Frequency
Figure 29. 0.1 Hz to 10 Hz Input
Voltage Noise
80
70
60
50
40
30
20
90
VSY = 2.5V
VOLTAGE NOISE DENSITY – nV/ Hz
VSY = 15V
VOLTAGE NOISE DENSITY – nV/ Hz
VOLTAGE NOISE DENSITY – nV/ Hz
Figure 30. 0.1 Hz to 10 Hz Input
Voltage Noise
90
90
80
70
60
50
40
30
20
10
10
0
50
100
150
FREQUENCY – Hz
200
0
250
Figure 31. Voltage Noise Density
100
200
300
FREQUENCY – Hz
400
SHORT CIRCUIT CURRENT – mA
30
25
20
15
10
5
0
0
500
1k
1.5k
FREQUENCY – Hz
2.0k
2.5k
Figure 34. Voltage Noise Density
60
50
40
30
20
100
200
300
FREQUENCY – Hz
50
30
20
ISC
10
0
10
20
ISC+
30
400
500
Figure 33. Voltage Noise Density
VSY = 5V
40
35
70
0
50
VSY = 2.5V
VSY = 15V
80
10
500
Figure 32. Voltage Noise Density
40
VOLTAGE NOISE DENSITY – nV/ Hz
TIME – 1s/DIV
TIME – 1s/DIV
VSY = 15V
40
SHORT CIRCUIT CURRENT – mA
0
30
20
ISC
10
0
10
20
30
ISC+
40
40
50
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
50
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
Figure 35. Short Circuit Current vs.
Temperature
Figure 36. Short Circuit Current vs.
Temperature
–8–
REV. 0
OP777
160
4.94
150
OUTPUT VOLTAGE LOW – mV
OUTPUT VOLTAGE HIGH – V
VSY = 5V
IL = 1mA
4.93
4.92
4.91
4.90
14.964
VSY = 5V
IL = 1mA
14.962
OUTPUT VOLTAGE HIGH – V
4.95
140
130
120
110
100
90
80
Figure 37. Output Voltage High vs.
Temperature
14.935
Figure 38. Output Voltage Low vs.
Temperature
1.5
VSY = 15V
IL = 1mA
14.940
14.945
0.5
0
14.950
0.5
14.955
1.0
14.960
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
1.5
Figure 40. Output Voltage Low vs.
Temperature
REV. 0
VSY = 15V
VCM = 0V
TA = 25C
1.0
VOS – V
OUTPUT VOLTAGE LOW – V
14.930
0
14.960
14.958
14.956
14.954
14.952
14.950
14.948
14.946
70
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
4.89
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
VSY = 15V
IL = 1mA
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TIME – Minutes
Figure 41. Warm-Up Drift
–9–
14.944
60 40 20 0 20 40 60 80 100 120 140
TEMPERATURE – C
Figure 39. Output Voltage High vs.
Temperature
OP777
BASIC OPERATION
100k
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.
100k
+3V
0.27V
100k
OP777
100k
0.1V
VIN = 1kHz at 400mV p-p
Figure 43. OP777 Configured as a Difference Amplifier
Operating at VCM < 0 V
Input Over Voltage Protection
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.
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 voltages 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.
When the input of an amplifier is more than a diode drop below
VEE, 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.
30V
OP777
V p-p = 32 V
VOUT
VIN
0V
VSY = 15V
VOLTAGE – 5V/DIV
VOLTAGE – 100V/DIV
Figure 44a. Unity Gain Follower
VIN
VOUT
TIME – 0.2ms/DIV
Figure 42. Input and Output Signals with VCM < 0 V
TIME – 400s/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 compensation 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.
VSY = 15V
VOLTAGE – 5V/DIV
VIN
VOUT
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 equivalent 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:
 R2

VOUT = 5 V − 
× RSENSE × I L 
 R1

TIME – 400s/DIV
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.
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, decreasing from VEE.
5V
2.49k
VOUT
Q1
5V
2.7V TO 30V
OP777
100
VOUT = 1mV
VIN = 1mV
0.1
OP777
RSENSE
Figure 48. A Low-Side Load Current Monitor
VOLTAGE – 25mV/DIV
Figure 46. Follower Circuit
1.0mV
TIME – 10s/DIV
Figure 47. Rail-to-Rail Operation
REV. 0
RETURN TO
GROUND
–11–
OP777
The OP777 can be very useful in many single supply bridge applications. 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.
6
REF
192
4
4
2.7V TO 30V
100k
100k
10.1k
1M
2.5V
REF
192
10pF
3
1M
OP777
R1 = 100k
0.1F
R2B
2.7k
15V
15V
3
R1(1+)
V1
R1
10pF
IO
10.1k
R2 = R2A + R2B
VO
OP777
R1(1+)
IO =
OP777
R1
C3865–2.5–4/00 (rev. 0) 01536
2
OP777
VL ≤ VSAT − VS
= 300
AR1VREF
VO =
+ 2.5V
2R2
R1
=
R1
RG = 10k
15V
2
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:
R2
+
R2A
97.3k
R2
V
R1 R2B S
VL
= 1mA 11mA
V2
RLOAD
Figure 51. Single Supply Current Source
Figure 49. Linear Response Bridge, Single Supply
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.
A single supply instrumentation amplifier using two OP777 amplifiers is shown in Figure 52.
15V
10.1k
R2 = 1M
2.7V TO 30V
1k
REF
192
R1 = 10.1k
OP777
VO
OP777
R2
12k
OP777
V1
3
20k
R1
V2
VO = 100 (V2 V1)
0.02mV V1 V2
2mV VOUT 29V
VO
R
R(1+)
+15V
+15V
R1
OP777
15V
USE MATCHED RESISTORS
R2
V
R1 REF
R
=
R
VO =
OP777
15V
290mV
Figure 52. Single Supply Micropower Instrumentation
Amplifier
Figure 50. Linear Response Bridge
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead SOIC
(RM Suffix)
8-Lead SOIC
(R Suffix)
0.122 (3.10)
0.114 (2.90)
8
0.1968 (5.00)
0.1890 (4.80)
8
5
0.1574 (4.00)
0.1497 (3.80) 1
0.199 (5.05)
0.187 (4.75)
0.122 (3.10)
0.114 (2.90)
1
5
4
0.2440 (6.20)
0.2284 (5.80)
4
PIN 1
0.0098 (0.25)
0.0040 (0.10)
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.006 (0.15)
0.002 (0.05)
0.018 (0.46)
SEATING 0.008 (0.20)
PLANE
0.120 (3.05)
0.112 (2.84)
0.043 (1.09)
0.037 (0.94)
0.011 (0.28)
0.003 (0.08)
33
27
0.0688 (1.75)
0.0532 (1.35)
0.0500 0.0192 (0.49)
SEATING (1.27)
0.0098 (0.25)
PLANE BSC 0.0138 (0.35) 0.0075 (0.19)
0.0196 (0.50)
x 45°
0.0099 (0.25)
8°
0° 0.0500 (1.27)
0.0160 (0.41)
0.028 (0.71)
0.016 (0.41)
–12–
REV. 0
PRINTED IN U.S.A.
4
2.7V TO 30V
1M
2N2222