PIN CONNECTIONS
8-Lead Narrow-Body SO
8-Lead Epoxy DIP
(S Suffix)
(P Suffix)
OUT A
IN A
+IN A
V
V+
OUT B
IN B
+IN B
1
2
3
4
5
6
7
8
OP295
OUT A
IN A
+IN A
V
V+
OUT B
IN B
+IN B
1
2
3
4
5
6
7
8
OP295
14-Lead Epoxy DIP
16-Lead SO (300 Mil)
(P Suffix)
(S Suffix)
1
2
3
4
5
6
7
14
13
12
11
10
9
8
OUT A
IN A
+IN A
V+
+IN B
IN B
OUT B
IN D
+IN D
V
+IN C
IN C
OUT C
OUT D
OP495
TOP VIEW
(Not to Scale)
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
NC = NO CONNECT
OUT A
IN A
+IN A
V+
+IN B
IN B
OUT B
NC
OUT D
IN D
+IN D
V
+IN C
IN C
OUT C
NC
OP495
a
Dual/Quad Rail-to-Rail
Operational Amplifiers
OP295/OP495
FEATURES
Rail-to-Rail Output Swing
Single-Supply Operation: 3 V to 36 V
Low Offset Voltage: 300 V
Gain Bandwidth Product: 75 kHz
High Open-Loop Gain: 1,000 V/mV
Unity-Gain Stable
Low Supply Current/Per Amplifier: 150 A max
APPLICATIONS
Battery-Operated Instrumentation
Servo Amplifiers
Actuator Drives
Sensor Conditioners
Power Supply Control
GENERAL DESCRIPTION
Rail-to-rail output swing combined with dc accuracy are the key
features of the OP495 quad and OP295 dual CBCMOS operational
amplifiers. By using a bipolar front end, lower noise and higher
accuracy than that of CMOS designs has been achieved. Both input
and output ranges include the negative supply, providing the user
"zero-in/zero-out" capability. For users of 3.3 V systems such as
lithium batteries, the OP295/OP495 is specified for 3 V operation.
Maximum offset voltage is specified at 300
mV for 5 V operation,
and the open-loop gain is a minimum of 1000 V/mV. This yields
performance that can be used to implement high accuracy systems,
even in single-supply designs.
The ability to swing rail-to-rail and supply 15 mA to the load makes
the OP295/OP495 an ideal driver for power transistors and "H"
bridges. This allows designs to achieve higher efficiencies and to
transfer more power to the load than previously possible without
the use of discrete components. For applications that require
driving inductive loads, such as transformers, increases in efficiency
are also possible. Stability while driving capacitive loads is another
benefit of this design over CMOS rail-to-rail amplifiers. This is
useful for driving coax cable or large FET transistors. The
OP295/OP495 is stable with loads in excess of 300 pF.
The OP295 and OP495 are specified over the extended industrial
(40
C to +125C) temperature range. OP295s are available in
8-lead plastic DIP plus SO-8 surface-mount packages. OP495s are
available in 14-lead plastic and SO-16 surface-mount packages.
Contact your local sales office for MIL-STD-883 data sheet.
REV. C
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. 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
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2002
REV. C
2
OP295/OP495SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
V
OS
30
300
mV
40
C T
A
+125C
800
mV
Input Bias Current
I
B
8
20
nA
40
C T
A
+125C
30
nA
Input Offset Current
I
OS
1
3
nA
40
C T
A
+125C
5
nA
Input Voltage Range
V
CM
0
4.0
V
Common-Mode Rejection Ratio
CMRR
0 V
V
CM
4.0 V, 40C T
A
+125C
90
110
dB
Large Signal Voltage Gain
A
VO
R
L
= 10 k
W, 0.005 V
OUT
4.0 V
1,000
10,000
V/mV
R
L
= 10 k
W, 40C T
A
+125C
500
V/mV
Offset Voltage Drift
DV
OS
/
DT
1
5
mV/C
OUTPUT CHARACTERISTICS
Output Voltage Swing High
V
OH
R
L
= 100 k
W to GND
4.98
5.0
V
R
L
= 10 k
W to GND
4.90
4.94
V
I
OUT
= 1 mA, 40
C T
A
+125C
4.7
V
Output Voltage Swing Low
V
OL
R
L
= 100 k
W to GND
0.7
2
mV
R
L
= 10 k
W to GND
0.7
2
mV
I
OUT
= 1 mA, 40
C T
A
+125C
90
mV
Output Current
I
OUT
11
18
mA
POWER SUPPLY
Power Supply Rejection Ratio
PSRR
1.5 V V
S
15 V
90
110
dB
1.5 V V
S
15 V,
40
C T
A
+125C
85
dB
Supply Current Per Amplifier
I
SY
V
OUT
= 2.5 V, R
L
=
, 40C T
A
+125C
150
mA
DYNAMIC PERFORMANCE
Skew Rate
SR
R
L
= 10 k
W
0.03
V/
ms
Gain Bandwidth Product
GBP
75
kHz
Phase Margin
q
O
86
Degrees
NOISE PERFORMANCE
Voltage Noise
e
n
p-p
0.1 Hz to 10 Hz
1.5
mV p-p
Voltage Noise Density
e
n
f = 1 kHz
51
nV/
Hz
Current Noise Density
i
n
f = 1 kHz
<0.1
pA/
Hz
Specifications subject to change without notice.
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
V
OS
30
500
mV
Input Bias Current
I
B
8
20
nA
Input Offset Current
I
OS
1
3
nA
Input Voltage Range
V
CM
0
2.0
V
Common-Mode Rejection Ratio
CMRR
0 V
V
CM
2.0 V, 40C T
A
+125C
90
110
dB
Large Voltage Gain
A
VO
R
L
= 10 k
W
750
V/mV
Offset Voltage Drift
DV
OS
/
DT
1
mV/C
OUTPUT CHARACTERISTICS
Output Voltage Swing High
V
OH
R
L
= 10 k
W to GND
2.9
V
Output Voltage Swing Low
V
OL
R
L
= 10 k
W to GND
0.7
2
mV
POWER SUPPLY
Power Supply Rejection Ratio
PSRR
1.5 V V
S
15 V
90
110
dB
1.5 V V
S
15 V,
40
C T
A
+125C
85
dB
Supply Current Per Amplifier
I
SY
V
OUT
= 1.5 V, R
L
=
, 40C T
A
+125C
150
mA
DYNAMIC PERFORMANCE
Slew Rate
SR
R
L
= 10 k
W
0.03
V/
ms
Gain Bandwidth Product
GBP
75
kHz
Phase Margin
q
O
85
Degrees
NOISE PERFORMANCE
Voltage Noise
e
n
p-p
0.1 Hz to 10 Hz
1.6
mV p-p
Voltage Noise Density
e
n
f = 1 kHz
53
nV/
Hz
Current Noise Density
i
n
f = 1 kHz
<0.1
pA/
Hz
Specifications subject to change without notice.
(@ V
S
= 5.0 V, V
CM
= 2.5 V, T
A
= 25 C unless otherwise noted.)
(@ V
S
= 3.0 V, V
CM
= 1.5 V, T
A
= 25 C unless otherwise noted.)
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
V
OS
30
300
mV
40
C T
A
+125C
800
mV
Input Bias Current
I
B
V
CM
= 0 V
7
20
nA
V
CM
= 0 V, 40
C T
A
+125C
30
nA
Input Offset Current
I
OS
V
CM
= 0 V
1
3
nA
V
CM
= 0 V, 40
C T
A
+125C
5
nA
Input Voltage Range
V
CM
15
13.5
V
Common-Mode Rejection Ratio
CMRR
15.0 V
V
CM
+13.5 V, 40C T
A
+125C
90
110
dB
Large Signal Voltage Gain
A
VO
R
L
= 10 k
W
1,000
4,000
V/mV
Offset Voltage Drift
DV
OS
/
DT
1
mV/C
OUTPUT CHARACTERISTICS
Output Voltage Swing High
V
OH
R
L
= 100 k
W to GND
14.95
V
R
L
= 10 k
W to GND
14.80
V
Output Voltage Swing Low
V
OL
R
L
= 100 k
W to GND
14.95
V
R
L
= 10 k
W to GND
14.85
V
Output Current
I
OUT
15
25
mA
POWER SUPPLY
Power Supply Rejection Ratio
PSRR
V
S
=
1.5 V to 15 V
90
110
dB
V
S
=
1.5 V to 15 V, 40C T
A
+125C
85
dB
Supply Current
I
SY
V
O
= 0 V, R
L
=
, V
S
=
18 V,
40
C T
A
+125C
175
mA
Supply Voltage Range
V
S
3 (
1.5)
36 (
18)
V
DYNAMIC PERFORMANCE
Slew Rate
SR
R
L
= 10 k
W
0.03
V/
ms
Gain Bandwidth Product
GBP
85
kHz
Phase Margin
q
O
83
Degrees
NOISE PERFORMANCE
Voltage Noise
e
n
p-p
0.1 Hz to 10 Hz
1.25
mV p-p
Voltage Noise Density
e
n
f =1 kHz
45
nV/
Hz
Current Noise Density
i
n
f = 1 kHz
<0.1
pA/
Hz
Specifications subject to change without notice.
OP295/OP495
REV. C
3
(@ V
S
=
15.0 V, T
A
= 25 C unless otherwise noted.)
REV. C
4
OP295/OP495
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18 V
Input Voltage
2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18 V
Differential Input Voltage
2
. . . . . . . . . . . . . . . . . . . . . . . . . 36 V
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range
P, S Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Operating Temperature Range
OP295G, OP495G . . . . . . . . . . . . . . . . . . . 40
C to +125C
Junction Temperature Range
P, S Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300
C
NOTES
1
Absolute maximum ratings apply to packaged parts, unless otherwise noted.
2
For supply voltages less than
18 V, the absolute maximum input voltage is
equal to the supply voltage.
Typical Performance Characteristics
140
20
100
80
40
25
60
50
120
100
75
50
25
0
TEMPERATURE C
SUPPL
Y CURRENT
A
V
S
= 5V
V
S
= 3V
V
S
= 36V
TPC 1. Supply Current Per Amplifier vs. Temperature
Package Type
JA
*
JC
Unit
8-Lead Plastic DIP (P)
103
43
C/W
8-Lead SOIC (S)
158
43
C/W
14-Lead Plastic DIP (P)
83
39
C/W
16-Lead SO (S)
98
30
C/W
*
q
JA
is specified for the worst case conditions, i.e.,
q
JA
is specified for device in
socket for cerdip, P-DIP, and LCC packages;
q
JA
is specified for device soldered
in circuit board for SOIC package.
ORDERING GUIDE
Temperature
Package
Package
Model
Range
Description
Option
OP295GP
40
C to +125C
8-Lead Plastic DIP
N-8
OP295GS
40
C to +125C
8-Lead SOIC
SO-8
OP495GP
40
C to +125C
14-Lead Plastic DIP
N-14
OP495GS
40
C to +125C
16-Lead SOL
R-16
15.2
15.2
100
14.6
15.0
25
14.8
50
14.2
14.4
14.4
14.6
14.8
15.0
75
50
25
0
TEMPERATURE C
OUTPUT SWING
V
+
OUTPUT SWING
V
V
S
= 15V
R
L
= 100k
R
L
= 2k
R
L
= 10k
R
L
= 2k
R
L
= 10k
R
L
= 100k
TPC 2. Output Voltage Swing vs. Temperature
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 OP295/OP495 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.
WARNING!
ESD SENSITIVE DEVICE
REV. C
5
OP295/OP495
3.10
2.50
100
2.80
2.60
25
2.70
50
3.00
2.90
75
50
25
0
TEMPERATURE C
OUTPUT
V
O
L
T
A
GE SWING
V
V
S
= 3V
R
L
= 2k
R
L
= 10k
R
L
= 100k
TPC 3. Output Voltage Swing vs. Temperature
200
0
250
50
25
200
250
100
75
125
150
175
200
150
100
50
0
50
100
150
V
S
= 5V
T
A
= 25 C
INPUT OFFSET VOLTAGE V
UNITS
BASED ON 600 OP AMPS
TPC 4. OP295 Input Offset (V
OS
) Distribution
UNITS
250
0
3.2
75
25
0.4
50
0
150
100
125
175
200
225
2.8
2.4
2.0
1.6
1.2
0.8
BASED ON 600 OP AMPS
V
S
= 5V
40 T
A
+85 C
T
C
V
OS
V/ C
TPC 5. OP295 TCV
OS
Distribution
5.10
4.50
100
4.80
4.60
25
4.70
50
5.00
4.90
75
50
25
0
TEMPERATURE C
OUTPUT
V
O
L
T
A
GE SWING
V
V
S
= 5V
R
L
= 2k
R
L
= 10k
R
L
= 100k
TPC 6. Output Voltage Swing vs. Temperature
500
0
300
150
50
50
100
100
300
200
250
350
400
450
250
200
150
100
50
0
INPUT OFFSET VOLTAGE V
UNITS
V
S
= 5V
T
A
= 25 C
BASED ON 1200 OP AMPS
TPC 7. OP495 Input Offset (V
OS
) Distribution
500
0
3.2
150
50
0.4
100
0
300
200
250
350
400
450
2.8
2.4
2.0
1.6
1.2
0.8
T
C
V
OS
V/ C
UNITS
V
S
= 5V
40 T
A
+85 C
BASED ON 1200 OP AMPS
TPC 8. OP495 TCV
OS
Distribution
REV. C
6
OP295/OP495
V
S
= 5V
20
0
100
12
4
25
8
50
16
75
50
25
0
TEMPERATURE C
INPUT BIAS CURRENT nA
TPC 9. Input Bias Current vs. Temperature
V
S
= 5V
TEMPERATURE C
40
0
100
10
5
25
50
20
15
25
30
35
75
50
25
0
V
S
= 15V
SOURCE
SINK
SOURCE
SINK
OUTPUT CURRENT mA
TPC 10. Output Current vs. Temperature
TEMPERATURE C
OPEN-LOOP GAIN
V/
V
R
L
= 2k
100
10
1
50
25
100
0
25
50
75
V
S
= 15V
V
O
= 10V
R
L
= 10k
R
L
= 100k
TPC 11. Open-Loop Gain vs. Temperature
12
0
100
6
2
25
4
50
10
8
75
50
25
0
TEMPERATURE C
OPEN-LOOP GAIN
V/
V
V
S
= 5V
V
O
= 4V
R
L
= 100k
R
L
= 10k
R
L
= 2k
TPC 12. Open-Loop Gain vs. Temperature
1V
100 V
1 A
10 A
10mA
1mA
100 A
100mV
10mV
1mV
LOAD CURRENT
OUTPUT V
O
L
T
A
GE
TO
RAIL
SOURCE
SINK
V
S
= 5V
T
A
= 25 C
TPC 13. Output Voltage to Supply Rail vs. Load Current
OP295/OP495
REV. C
7
APPLICATIONS
Rail-to-Rail Application Information
The OP295/OP495 has a wide common-mode input range extending
from ground to within about 800 mV of the positive supply.
There is a tendency to use the OP295/OP495 in buffer applications
where the input voltage could exceed the common-mode input
range. This may initially appear to work because of the high input
range and rail-to-rail output range. But above the common-mode
input range the amplifier is, of course, highly nonlinear. For this
reason it is always required that there be some minimal amount
of gain when rail-to-rail output swing is desired. Based on the
input common-mode range, this gain should be at least 1.2.
Low Drop-Out Reference
The OP295/OP495 can be used to gain up a 2.5 V or other low
voltage reference to 4.5 V for use with high resolution A/D convert-
ers that operate from 5 V only supplies. The circuit in Figure 1 will
supply up to 10 mA. Its no-load drop-out voltage is only 20 mV.
This circuit will supply over 3.5 mA with a 5 V supply.
16k
1/2
OP295/
OP495
V = 4.5V
OUT
1 F TO
10 F
10
0.001 F
20k
REF43
2
6
4
5V
5V
Figure 1. 4.5 V, Low Drop-Out Reference
Low Noise, Single-Supply Preamplifier
Most single-supply op amps are designed to draw low supply
current, at the expense of having higher voltage noise. This
tradeoff may be necessary because the system must be powered
by a battery. However, this condition is worsened because all
circuit resistances tend to be higher; as a result, in addition to
the op amp's voltage noise, Johnson noise (resistor thermal noise)
is also a significant contributor to the total noise of the system.
The choice of monolithic op amps that combine the characteris-
tics of low noise and single-supply operation is rather limited.
Most single-supply op amps have noise on the order of 30 nV/
Hz
to 60 nV/
Hz and single-supply amplifiers with noise below
5 nV/
Hz do not exist.
In order to achieve both low noise and low supply voltage opera-
tion, discrete designs may provide the best solution. The circuit
on Figure 2 uses the OP295/OP495 rail-to-rail amplifier and a
matched PNP transistor pair--the MAT03--to achieve zero-in/
zero-out single-supply operation with an input voltage noise of
3.1 nV/
Hz at 100 Hz. R5 and R6 set the gain of 1,000, making
this circuit ideal for maximizing dynamic range when amplifying
low level signals in single-supply applications. The OP295/OP495
provides rail-to-rail output swings, allowing this circuit to oper-
ate with 0 V to 5 V outputs. Only half of the OP295/OP495 is
used, leaving the other uncommitted op amp for use elsewhere.
10 F
0.1 F
R1
LED
V
IN
2
3
5
6
3
7
1
MAT-03
Q1
Q2
R7
510
C1
1500pF
R4
R8
100
R3
R2
27k
R5
10k
C2
10 F
V
OUT
OP295/OP495
R6
10
2
8
4
1
Q2
2N3906
Figure 2. Low Noise Single-Supply Preamplifier
The input noise is controlled by the MAT03 transistor pair and
the collector current level. Increasing the collector current reduces
the voltage noise. This particular circuit was tested with 1.85 mA
and 0.5 mA of current. Under these two cases, the input voltage
noise was 3.1 nV/
Hz and 10 nV/Hz, respectively. The high
collector currents do lead to a tradeoff in supply current, bias
current, and current noise. All of these parameters will increase
with increasing collector current. For example, typically the
MAT03 has an h
FE
= 165. This leads to bias currents of 11
mA
and 3
mA, respectively. Based on the high bias currents, this circuit
is best suited for applications with low source impedance such
as magnetic pickups or low impedance strain gages. Furthermore,
a high source impedance will degrade the noise performance.
For example, a 1 k
W resistor generates 4 nV/Hz of broadband
noise, which is already greater than the noise of the preamp.
The collector current is set by R1 in combination with the LED
and Q2. The LED is a 1.6 V Zener diode that has a temperature
coefficient close to that of Q2's base-emitter junction, which
provides a constant 1.0 V drop across R1. With R1 equal to 270
W,
the tail current is 3.7 mA and the collector current is half that, or
1.85 mA. The value of R1 can be altered to adjust the collector cur-
rent. Whenever R1 is changed, R3 and R4 should also be adjusted.
To maintain a common-mode input range that includes ground,
the collectors of the Q1 and Q2 should not go above 0.5 V--otherwise
they could saturate. Thus, R3 and R4 must be small enough to
prevent this condition. Their values and the overall performance
for two different values of R1 are summarized in Table I. Lastly,
the potentiometer, R8, is needed to adjust the offset voltage to
null it to zero. Similar performance can be obtained using an OP90
as the output amplifier with a savings of about 185
mA of supply
current. However, the output swing will not include the positive
rail, and the bandwidth will reduce to approximately 250 Hz.
REV. C
8
OP295/OP495
Table I. Single-Supply Low Noise Preamp Performance
I
C
= 1.85 mA
I
C
= 0.5 mA
R1
270
W
1.0 k
W
R3, R4
200
W
910
W
e
n
@ 100 Hz
3.15 nV/
Hz
8.6 nV/
Hz
e
n
@ 10 Hz
4.2 nV/
Hz
10.2 nV/
Hz
I
SY
4.0 mA
1.3 mA
I
B
11
mA
3
mA
Bandwidth
1 kHz
1 kHz
Closed-Loop Gain
1,000
1,000
Driving Heavy Loads
The OP295/OP495 is well suited to drive loads by using a
power transistor, Darlington or FET to increase the current to
the load. The ability to swing to either rail can assure that the
device is turned on hard. This results in more power to the load
and an increase in efficiency over using standard op amps with
their limited output swing. Driving power FETs is also possible
with the OP295/OP495 because of its ability to drive capacitive
loads of several hundred picofarads without oscillating.
Without the addition of external transistors, the OP295/OP495
can drive loads in excess of
15 mA with 15 V or +30 V
supplies. This drive capability is somewhat decreased at lower
supply voltages. At
5 V supplies, the drive current is 11 mA.
Driving motors or actuators in two directions in a single-supply
application is often accomplished using an "H" bridge. The prin-
ciple is demonstrated in Figure 3a. From a single 5 V supply this
driver is capable of driving loads from 0.8 V to 4.2 V in both direc-
tions. Figure 3b shows the voltages at the inverting and noninverting
outputs of the driver. There is a small crossover glitch that is frequency
dependent and would not cause problems unless this was a low
distortion application such as audio. If this is used to drive induc-
tive loads, be sure to add diode clamps to protect the bridge from
inductive kickback.
10k
1.67V
2N2222
2N2222
OUTPUTS
2N2907
2N2907
5V
0 V
IN
2.5V 5k
10k
10k
Figure 3a. "H" Bridge
10
90
100
0%
2V
2V
1ms
Figure 3b. "H" Bridge Outputs
Direct Access Arrangement
OP295/OP495 can be used in a single-supply Direct Access
Arrangement (DAA) as is shown in Figure 4. This figure shows
a portion of a typical DM capable of operating from a single 5 V
supply and it may also work on 3 V supplies with minor modifi-
cations. Amplifiers A2 and A3 are configured so that the transmit
signal TXA is inverted by A2 and is not inverted by A3. This arrange-
ment drives the transformer differentially so that the drive to the
transformer is effectively doubled over a single amplifier arrange-
ment. This application takes advantage of the OP295/OP495's
ability to drive capacitive loads, and to save power in single-supply
applications.
2.5V REF
A3
750pF
0.1 F
A1
37.4k
390pF
RXA
TXA
OP295/
OP495
OP295/
OP495
A2
OP295/
OP495
0.0047 F
3.3k
20k
475
22.1k
20k
0.1 F
20k
20k
20k
0.033 F
1:1
Figure 4. Direct Access Arrangement
A Single-Supply Instrumentation Amplifier
The OP295/OP495 can be configured as a single-supply instru-
mentation amplifier as in Figure 5. For our example, V
REF
is set
equal to
V
+
2
and V
O
is measured with respect to V
REF
. The input
common-mode voltage range includes ground and the output
swings to both rails.
V+
V
IN
V
REF
1
R1
100k
R2
R3
R4
V
O
V
IN
+ V
REF
V
O
= 5 +
200k
R
G
R
G
3
2
8
7
4
5
6
20k
20k
100k
1/2
OP295/
OP495
1/2
OP295/
OP495
Figure 5. Single-Supply Instrumentation Amplifier
Resistor R
G
sets the gain of the instrumentation amplifier. Mini-
mum gain is 6 (with no R
G
). All resistors should be matched in
absolute value as well as temperature coefficient to maximize
OP295/OP495
REV. C
9
common-mode rejection performance and minimize drift. This
instrumentation amplifier can operate from a supply voltage as
low as 3 V.
A Single-Supply RTD Thermometer Amplifier
This RTD amplifier takes advantage of the rail-to-rail swing of
the OP295/OP495 to achieve a high bridge voltage in spite of a
low 5 V supply. The OP295/OP495 amplifier servos a constant
200
mA current to the bridge. The return current drops across
the parallel resistors 6.19 k
W and the 2.55 MW, developing a
voltage that is servoed to 1.235 V, which is established by the
AD589 bandgap reference. The 3-wire RTD provides an equal
line resistance drop in both 100
W legs of the bridge, thus improving
the accuracy.
The AMP04 amplifies the differential bridge signal and converts it
to a single-ended output. The gain is set by the series resistance of
the 332
W resistor plus the 50 W potentiometer. The gain scales the
output to produce a 4.5 V full scale. The 0.22
mF capacitor to the
output provides a 7 Hz low-pass filter to keep noise at a minimum.
ZERO ADJ
200
10-TURNS
26.7k
0.5%
26.7k
0.5%
100
RTD
100
0.5%
2.55M
1%
6.19k
1%
AD589
37.4k
5V
1.235
1
2
3
1/2
OP295/
OP495
3
2
4
5
6
8
1
7
5V
AMP04
50
332
0.22 F
V
O
4.5V = 450 C
0V = 0 C
Figure 6. Low Power RTD Amplifier
A Cold Junction Compensated, Battery-Powered
Thermocouple Amplifier
The OP295/OP495's 150
mA quiescent current per amplifier
consumption makes it useful for battery-powered temperature
measuring instruments. The K-type thermocouple terminates
into an isothermal block where the terminated junctions' ambi-
ent temperatures can be continuously monitored and corrected
by summing an equal but opposite thermal EMF to the ampli-
fier, thereby canceling the error introduced by the cold junctions.
ISOTHERMAL
BLOCK
AD589
ALUMEL
CHROMEL
AL
CR
K-TYPE
THERMOCOUPLE
40.7 V/ C
COLD
JUNCTIONS
1N914
1.5M
1%
24.9k
1%
7.15k
1%
24.3k
1%
4.99k
1%
475
1%
2.1k
1%
ZERO
ADJUST
500
10-TURN
OP295/
OP495
24.9k
1.235V
9V
1.33M
20k
1
2
3
4
8
SCALE
ADJUST
V
O
5V = 500 C
0V = 0 C
Figure 7. Battery-Powered, Cold-Junction Compensated
Thermocouple Amplifier
To calibrate, immerse the thermocouple measuring junction in a
0
C ice bath, adjust the 500 W Zero Adjust pot to zero volts out.
Then immerse the thermocouple in a 250
C temperature bath
or oven and adjust the Scale Adjust pot for an output voltage of
2.50 V, which is equivalent to 250
C. Within this temperature
range, the K-type thermocouple is quite accurate and produces
a fairly linear transfer characteristic. Accuracy of
3C is achiev-
able without linearization.
Even if the battery voltage is allowed to decay to as low as 7 V, the
rail-to-rail swing allows temperature measurements to 700
C.
However, linearization may be necessary for temperatures above
250
C where the thermocouple becomes rather nonlinear. The
circuit draws just under 500
mA supply current from a 9 V battery.
A 5 V Only, 12-Bit DAC That Swings 0 V to 4.095 V
Figure 8 shows a complete voltage output DAC with wide output
voltage swing operating off a single 5 V supply. The serial input
12-bit D/A converter is configured as a voltage output device with
the 1.235 V reference feeding the current output pin (I
OUT
) of the
DAC. The V
REF
which is normally the input now becomes the output.
The output voltage from the DAC is the binary weighted voltage
of the reference, which is gained up by the output amplifier such
that the DAC has a 1 mV per bit transfer function.
5V
5V
R1
17.8k
1.23V
AD589
3
4
7
6
5
GND CLK SRI LD
V
DD
V
REF
R
FB
2
1
3
2
4
1
8
DIGITAL
CONTROL
5V
OP295/
OP495
R3
5k
R2
41.2k
R4
100k
D
4096
V
O
=
(4.096V)
TOTAL POWER DISSIPATION = 1.6mW
I
OUT
8
DAC8043
Figure 8. A 5 V 12-Bit DAC with 0 V to 4.095 Output Swing
4 mA to 20 mA Current Loop Transmitter
Figure 9 shows a self powered 4 mA to 20 mA current loop
transmitter. The entire circuit floats up from the single-supply
(12 V to 36 V) return. The supply current carries the signal within
the 4 mA to 20 mA range. Thus the 4 mA establishes the baseline
current budget with which the circuit must operate. This circuit
consumes only 1.4 mA maximum quiescent current, making 2.6 mA
of current available to power additional signal conditioning circuitry
or to power a bridge circuit.
5V
6
2
4
REF02
GND
100
220
2N1711
4mA
TO
20mA
R
L
100
100
1%
1
8
3
2
4
1/2
OP295/
OP495
100k
1%
220pF
HP
5082-2800
100k
10-TURN
1.21M
1%
182k
1%
10k
10-TURN
V
IN
0 + 3V
12V
TO
36V
SPAN ADJ
NULL ADJ
Figure 9. 4 mA to 20 mA Current Loop Transmitter
REV. C
10
OP295/OP495
A 3 V Low-Dropout Linear Voltage Regulator
Figure 10 shows a simple 3 V voltage regulator design. The
regulator can deliver 50 mA load current while allowing a 0.2 V
dropout voltage. The OP295/OP495's rail-to-rail output swing
handily drives the MJE350 pass transistor without requiring special
drive circuitry. At no load, its output can swing less than the pass
transistor's base-emitter voltage, turning the device nearly off. At
full load, and at low emitter-collector voltages, the transistor beta
tends to decrease. The additional base current is easily handled
by the OP295/OP495 output.
The amplifier servos the output to a constant voltage, which
feeds a portion of the signal to the error amplifier.
Higher output current, to 100 mA, is achievable at a higher
dropout voltage of 3.8 V.
V
IN
5V TO 3.2V
MJE 350
1/2
OP295/
OP495
43k
AD589
1.235V
30.9k
1%
44.2k
1%
3
2
4
1
8
1000pF
I
L
< 50mA
V
O
100 F
Figure 10. 3 V Low Dropout Voltage Regulator
Figure 11 shows the regulator's recovery characteristic when its
output underwent a 20 mA to 50 mA step current change.
10
100
0%
90
1ms
20mV
2V
50mA
20mA
OUTPUT
STEP
CURRENT
CONTROL
WAVEFORM
Figure 11. Output Step Load Current Recovery
Low-Dropout, 500 mA Voltage Regulator with Fold-Back
Current Limiting
Adding a second amplifier in the regulation loop as shown in
Figure 12 provides an output current monitor as well as fold-
back current limiting protection.
Amplifier A1 provides error amplification for the normal voltage
regulation loop. As long as the output current is less than 1 A,
amplifier A2's output swings to ground, reverse biasing the di-
ode and effectively taking itself out of the circuit. However, as
the output current exceeds 1 amp, the voltage that develops
across the 0.1
W sense resistor forces the amplifier A2's output
to go high, forward-biasing the diode, which in turn closes the
current limit loop. At this point A2's lower output resistance
dominates the drive to the power MOSFET transistor, thereby
effectively removing the A1 voltage regulation loop from the circuit.
If the output current greater than 1 amp persists, the current limit
loop forces a reduction of current to the load, which causes a
corresponding drop in output voltage. As the output voltage
drops, the current limit threshold also drops fractionally, resulting
in a decreasing output current as the output voltage decreases,
to the limit of less than 0.2 A at 1 V output. This "fold-back"
effect reduces the power dissipation considerably during a short
circuit condition, thus making the power supply far more forgiving
in terms of the thermal design requirements. Small heat sinking
on the power MOSFET can be tolerated.
The OP295's rail-to-rail swing exacts higher gate drive to the
power MOSFET, providing a fuller enhancement to the transistor.
The regulator exhibits 0.2 V dropout at 500 mA of load current.
At 1 amp output, the dropout voltage is typically 5.6 V.
IRF9531
S
D
G
6V
100k
5%
REF43
2
4
6
2.500V
124k
1%
124k
1%
205k
1%
45.3k
1%
45.3k
1%
210k
1%
R
SENSE
0.1
1/4W
A2
A1
1
4
2
3
5
6
7
8
1/2
OP295/
OP495
1/2
OP295/
OP495
1N4148
0.01 F
I
O
(NORM) = 0.5A
I
O
(MAX) = 1A
5V V
O
Figure 12. Low Dropout, 500 mA Voltage Regulator with
Fold-Back Current Limiting
Square Wave Oscillator
The circuit in Figure 13 is a square wave oscillator (note the
positive feedback). The rail-to-rail swing of the OP295/OP495
helps maintain a constant oscillation frequency even if the supply
voltage varies considerably. Consider a battery powered system
where the voltages are not regulated and drop over time. The
rail-to-rail swing ensures that the noninverting input sees the full
V+/2, rather than only a fraction of it.
The constant frequency comes from the fact that the 58.7 k
W
feedback sets up Schmitt Trigger threshold levels that are directly
proportional to the supply voltage, as are the RC charge voltage
levels. As a result, the RC charge time, and therefore, the frequency,
remains constant independent of supply voltage. The slew rate
of the amplifier limits oscillation frequency to a maximum of
about 800 Hz at a 5 V supply.
Single-Supply Differential Speaker Driver
Connected as a differential speaker driver, the OP295/OP495
can deliver a minimum of 10 mA to the load. With a 600
W
load, the OP295/OP495 can swing close to 5 V peak-to-peak
across the load.
OP295/OP495
REV. C
11
V+
100k
58.7k
R
1/2
OP295/
OP495
FREQ OUT
4
1
8
3
2
100k
F
OSC
=
1
RC
< 350Hz @ V+ = 5V
C
Figure 13. Square Wave Oscillator Has Stable Frequency
Regardless of Supply Changes
10k
90.9k
90.9k
V+
1/4
OP295/
OP495
1/4
OP295/
OP495
1/4
OP295/
OP495
100k
10k
20k
20k
V
IN
2.2 F
V+
SPEAKER
Figure 14. Single-Supply Differential Speaker Driver
High Accuracy, Single-Supply, Low Power Comparator
The OP295/OP495 makes an accurate open-loop comparator.
With a single 5 V supply, the offset error is less than 300
mV. Figure
15 shows the OP295/OP495's response time when operating
open-loop with 4 mV overdrive. It exhibits a 4 ms response time at
the rising edge and a 1.5 ms response time at the falling edge.
10
100
0%
90
5ms
2V
1V
OUTPUT
(5mV OVERDRIVE
@ OP-295 INPUT)
INPUT
Figure 15. Open-Loop Comparator Response Time with
5 mV Overdrive
OP295/OP495 SPICE MODEL Macro-Model
* Node Assignments
*
Noninverting Input
*
Inverting Input
*
Positive Supply
*
Negative Supply
*
Output
*
*
.SUBCKT OP295
1
2
99
50
20
*
* INPUT STAGE
*
I1
99
4
2E-6
R1
1
6
5E3
R2
2
5
5E3
CIN
1
2
2E-12
IOS
1
2
0.5E-9
D1
5
3
DZ
D2
6
3
DZ
EOS
7
6
POLY (1) (31,39) 30E-6 0.024
Q1
8
5
4
QP
Q2
9
7
4
QP
R3
8
50
25.8E3
R4
9
50
25.8E3
*
* GAIN STAGE
*
R7
10
98
270E6
G1
98
10
POLY (1) (9,8) 4.26712E-9 27.8E-6
EREF 98
0
(39, 0) 1
R5
99
39
100E3
R6
39
50
100E3
*
* COMMON MODE STAGE
*
ECM
30
98
POLY(2) (1,39) (2,39) 0 0.5 0.5
R12
30
31
1E6
R13
31
98
100
*
* OUTPUT STAGE
*
I2
18
50
1.59E-6
V2
99
12
DC 2.2763
Q4
10
14
50
QNA
1.0
R11
14
50
33
M3
15
10
13
13
MN L=9E-6 W=102E-6 AD=15E-10 AD=15E-10
M4
13
10
50
50
MN L=9E-6 W=50E-6 AD=75E-11 AS=75E-11
D8
10
22
DX
V3
22
50
DC 6
M2
20
10
14
14
MN L=9E-6 W=2000E-6 AD=30E-9 AS=30E-9
Q5
17
17
99
QPA
1.0
Q6
18
17
99
QPA
4.0
R8
18
99
2.2E6
Q7
18
19
99
QPA
1.0
R9
99
19
8
C2
18
99
20E-12
M6
15
12
17
99
MP L=9E-6 W=27E-6 AD=405E-12 AS=405E-12
M1
20
18
19
99
MP L=9E-6 W=2000E-6 AD=30E-9 AS=30E-9
D4
21
18
DX
V4
99
21
DC 6
R10
10
11
6E3
C3
11
20
50E-12
.MODEL QNA NPN (IS=1.19E-16 BF=253 NF=0.99 VAF=193 IKF=2.76E-3
+ ISE=2.57E-13 NE=5 BR=0.4 NR=0.988 VAR=15 IKR=1.465E-4
+ ISC=6.9E-16 NC=0.99 RB=2.0E3 IRB=7.73E-6 RBM=132.8 RE=4
RC=209
+ CJE=2.1E-13 VJE=0.573 MJE=0.364 FC=0.5 CJC=1.64E-13 VJC=0.534
MJC=0.5
+ CJS=1.37E-12 VJS=0.59 MJS=0.5 TF=0.43E-9 PTF=30)
.MODEL QPA PNP (IS=5.21E-17 BF=131 NF=0.99 VAF=62 IKF=8.35E-4
+ ISE=1.09E-14 NE=2.61 BR=0.5 NR=0.984 VAR=15 IKR=3.96E-5
+ ISC=7.58E-16 NC=0.985 RB=1.52E3 IRB=1.67E-5 RBM=368.5 RE=6.31
RC=354.4
+ CJE=1.1E-13 VJE=0.745 MJE=0.33 FC=0.5 CJC=2.37E-13 VJC=0.762
MJC=0.4
+ CJS =7.11E-13 VJS=0.45 MJS=0.412 TF=1.0E-9 PTF=30)
.MODEL MN NMOS (LEVEL=3 VTO=1.3 RS=0.3 RD=0.3
+ TOX=8.5E-8 LD=1.48E-6 NSUB=1.53E16 UO=650 DELTA=10 VMAX=2E5
+ XJ=1.75E-6 KAPPA=0.8 ETA=0.066 THETA=0.01 TPG=1 CJ=2.9E-4
PB=0.837
+ MJ=0.407 CJSW=0.5E-9 MJSW=0.33)
.MODEL MP PMOS (LEVEL=3 VTO=1.1 RS=0.7 RD=0.7
+ TOX=9.5E-8 LD=1.4E-6 NSUB=2.4E15 UO=650 DELTA=5.6 VMAX=1E5
+ XJ=1.75E-6 KAPPA=1.7 ETA=0.71 THETA=5.9E-3 TPG=1 CJ=1.55E-4
PB=0.56
+ MJ=0.442 CJSW=0.4E-9 MJSW=0.33)
.MODEL DX D(IS=1E-15)
.MODEL DZ D (IS=1E-15, BV=7)
.MODEL QP PNP (BF=125)
.ENDS
REV. C
12
OP295/OP495
C0033104/02(C)
PRINTED IN U.S.A.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm)
8-Lead Plastic DIP
(P Suffix)
SEATING
PLANE
0.060 (1.52)
0.015 (0.38)
0.210
(5.33)
MAX
0.022 (0.558)
0.014 (0.356)
0.160 (4.06)
0.115 (2.93)
0.070 (1.77)
0.045 (1.15)
0.130
(3.30)
MIN
8
1
4
5
PIN 1
0.280 (7.11)
0.240 (6.10)
0.100 (2.54)
BSC
0.430 (10.92)
0.348 (8.84)
0.195 (4.95)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
0.325 (8.25)
0.300 (7.62)
14-Lead Plastic DIP
(P Suffix)
14
1
7
8
PIN 1
0.795 (20.19)
0.725 (18.42)
0.280 (7.11)
0.240 (6.10)
0.100 (2.54)
BSC
SEATING
PLANE
0.060 (1.52)
0.015 (0.38)
0.210 (5.33)
MAX
0.022 (0.558)
0.014 (0.356)
0.160 (4.06)
0.115 (2.93)
0.070 (1.77)
0.045 (1.15)
0.130
(3.30)
MIN
0.195 (4.95)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
0.325 (8.25)
0.300 (7.62)
8-Lead Narrow-Body SO
(S Suffix)
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
0
0.0196 (0.50)
0.0099 (0.25)
45
8
5
4
1
0.1968 (5.00)
0.1890 (4.80)
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.0500 (1.27)
BSC
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
16-Lead Wide-Body SO
(S Suffix)
SEATING
PLANE
0.0118 (0.30)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.1043 (2.65)
0.0926 (2.35)
0.050 (1.27)
BSC
16
9
8
1
0.4193 (10.65)
0.3937 (10.00)
0.2992 (7.60)
0.2914 (7.40)
PIN 1
0.4133 (10.50)
0.3977 (10.00)
0.0125 (0.32)
0.0091 (0.23)
8
0
0.0291 (0.74)
0.0098 (0.25)
45
0.0500 (1.27)
0.0157 (0.40)
Revision History
Location
Page
03/02--Data Sheet changed from REV. B to REV. C.
Figure changes to PIN CONNECTIONS ..................................................................................................................................... 1
Deletion of OP295GBC and OP495GBC from ORDERING GUIDE .......................................................................................... 3
Deletion of WAFER TEST LIMITS table .................................................................................................................................... 3
Changes to ABSOLUTE MAXIMUM RATINGS........................................................................................................................ 4
Deletion of DICE CHARACTERISTICS .................................................................................................................................... 4
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