1
®
OPA241, 2241, 4241
OPA251, 2251, 4251
®
OPA251
OPA2251
OPA4251
© 1997 Burr-Brown Corporation PDS-1406B Printed in U.S.A. October, 1998
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
Single-Supply,
Micro
POWER
OPERATIONAL AMPLIFIERS
FEATURES
●
Micro
POWER: IQ = 25µA
●SINGLE-SUPPLY OPERATION
●RAIL-TO-RAIL OUTPUT (within 50mV)
●WIDE SUPPLY RANGE
Single Supply: +2.7V to +36V
Dual Supply: ±1.35V to ±18V
●LOW OFFSET VOLTAGE: ±250µV max
●HIGH COMMON-MODE REJECTION: 124dB
●HIGH OPEN-LOOP GAIN: 128dB
●SINGLE, DUAL, AND QUAD
DESCRIPTION
The OPA241 series and OPA251 series are specifically
designed for battery powered, portable applications. In addi-
tion to very low power consumption (25µA), these amplifi-
ers feature low offset voltage, rail-to-rail output swing, high
common-mode rejection, and high open-loop gain.
The OPA241 series is optimized for operation at low power
supply voltage while the OPA251 series is optimized for
high power supplies. Both can operate from either single
(+2.7V to +36V) or dual supplies (±1.35V to ±18V). The
input common-mode voltage range extends 200mV below
the negative supply—ideal for single-supply applications.
They are unity-gain stable and can drive large capacitive
loads. Special design considerations assure that these prod-
ucts are easy to use. High performance is maintained as the
amplifiers swing to their specified limits. Because the initial
offset voltage (±250µV max) is so low, user adjustment is
usually not required. However, external trim pins are pro-
vided for special applications (single versions only).
The OPA241 and OPA251 (single versions) are available
in standard 8-pin DIP and SO-8 surface-mount packages.
The OPA2241 and OPA2251 (dual versions) come in 8-pin
DIP and SO-8 surface-mount packages. The OPA4241 and
OPA4251 (quad versions) are available in 14-pin DIP and
SO-14 surface-mount packages. All are fully specified
from –40°C to +85°C and operate from –55°C to +125°C.
APPLICATIONS
● BATTERY OPERATED INSTRUMENTS
● PORTABLE DEVICES
● MEDICAL INSTRUMENTS
●TEST EQUIPMENT
OPA241
OPA2241
OPA4241
1
2
3
4
8
7
6
5
NC
V+
Output
Offset Trim
Offset Trim
–In
+In
V–
OPA241, OPA251
8-Pin DIP, SO-8
1
2
3
4
8
7
6
5
V+
Out B
–In B
+In B
Out A
–In A
+In A
V–
OPA2241, OPA2251
8-Pin DIP, SO-8
A
B
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Out D
–In D
+In D
V–
+In C
–In C
Out C
Out A
–In A
+In A
V+
+In B
–In B
Out B
OPA4241, OPA4251
14-Pin DIP, SO-14
AD
BC
OPA241 Family optimized for +5V supply.
OPA251 Family optimized for ±15V supply.
OPA241 OPA4251
OPA4241
OPA2251
2
®
OPA241, 2241, 4241
OPA251, 2251, 4251
OPA241UA, PA OPA251UA, PA
OPA2241UA, PA OPA2251UA, PA
OPA4241UA, PA OPA4251UA, PA
PARAMETER CONDITION MIN TYP(1) MAX MIN TYP(1) MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage VOS ±50 ±250 ±100 µV
TA = –40°C to +85°C±100 ±400 ±130 µV
vs Temperature dVOS/dT TA = –40°C to +85°C±0.4 ±0.6 µV/°C
vs Power Supply PSRR VS = 2.7V to 36V 3 30 ✻✻µV/V
TA = –40°C to +85°CVS = 2.7V to 36V 30 ✻µV/V
Channel Separation (dual, quad) 0.3 ✻µV/V
INPUT BIAS CURRENT
Input Bias Current(2) IB–4 –20 ✻nA
TA = –40°C to +85°C–25 nA
Input Offset Current IOS ±0.1 ±2✻nA
TA = –40°C to +85°C±2nA
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz 1 ✻µVp-p
Input Voltage Noise Density, f = 1kHz en45 ✻nV/√Hz
Current Noise Density, f = 1kHz in40 ✻fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range VCM –0.2
(V+) –0.8
V
Common-Mode Rejection Ratio CMRR VCM = –0.2V to (V+) –0.8V 80 106 ✻dB
TA = –40°C to +85°CVCM = 0V to (V+) –0.8V 80 dB
INPUT IMPEDANCE
Differential 107 || 2 ✻Ω || pF
Common-Mode 109 || 4 ✻Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL
RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV
100 120 ✻dB
TA = –40°C to +85°C
RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV
100 dB
RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV
100 120 ✻dB
TA = –40°C to +85°C
RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV
100 dB
FREQUENCY RESPONSE
Gain-Bandwidth Product GBW 35 ✻kHz
Slew Rate SR VS = 5V, G = 1 0.01 ✻V/µs
Overload Recovery Time VIN • G = VS60 ✻µs
OUTPUT
Voltage Output Swing from Rail(3) VORL = 100kΩ to VS/2, AOL ≥ 70dB 50 ✻mV
RL = 100kΩ to VS/2, AOL ≥ 100dB 75 100 ✻mV
TA = –40°C to +85°CRL = 100kΩ to VS/2, AOL ≥ 100dB 100 mV
RL = 10kΩ to VS/2, AOL ≥ 100dB 100 200 ✻mV
TA = –40°C to +85°CRL = 10kΩ to VS/2, AOL ≥ 100dB 200 mV
Short-Circuit Current ISC
Single Versions –24/+4 ✻mA
Dual, Quad Versions –30/+4 ✻mA
Capacitive Load Drive CLOAD See Typical Curve ✻
POWER SUPPLY
Specified Voltage Range VS
+2.7 to +5
✻V
Operating Voltage Range TA = –40°C to +85°C +2.7 +36 ✻✻V
Quiescent Current (per amplifier) IQIO = 0 ±25 ±30 ✻µA
TA = –40°C to +85°CIO = 0 ±36 µA
TEMPERATURE RANGE
Specified Range –40 +85 ✻✻°C
Operating Range –55 +125 ✻✻°C
Storage Range –55 +125 ✻✻°C
Thermal Resistance
θ
JA
8-Pin DIP 100 ✻°C/W
SO-8 Surface Mount 150 ✻°C/W
14-Pin DIP 80 ✻°C/W
SO-14 Surface Mount 100 ✻°C/W
✻ Specifications the same as OPA241UA, PA.
NOTES: (1) VS = +5V. (2) The negative sign indicates input bias current flows out of the input terminals. (3) Output voltage swings are measured between the
output and power supply rails.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
SPECIFICATIONS: VS = 2.7V to 5V
At TA = +25°C, RL = 100kΩ connected to VS/2, unless otherwise noted.
Boldface limits apply over the specified temperature range, TA = –40°C to +85°C.
3
®
OPA241, 2241, 4241
OPA251, 2251, 4251
PARAMETER CONDITION MIN TYP MAX MIN TYP MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage VOS ±100 ±50 ±250 µV
TA = –40°C to +85°C±150 ±100 ±300 µV
vs Temperature dVOS/dT TA = –40°C to +85°C±0.6 ±0.5 µV/°C
vs Power Supply PSRR VS = ±1.35V to ±18V ✻✻ 330µV/V
TA = –40°C to +85°CVS = ±1.35V to ±18V ✻30 µV/V
Channel Separation (dual, quad) ✻0.3 µV/V
INPUT BIAS CURRENT
Input Bias Current(1) IB✻–4 –20 nA
TA = –40°C to +85°C–25 nA
Input Offset Current IOS ✻±0.1 ±2nA
TA = –40°C to +85°C±2nA
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz ✻1µVp-p
Input Voltage Noise Density, f = 1kHz en✻45 nV/√Hz
Current Noise Density, f = 1kHz in✻40 fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range VCM
(V–) –0.2 (V+) –0.8
V
Common-Mode Rejection Ratio CMRR VCM = –15.2V to 14.2V ✻100 124 dB
TA = –40°C to +85°CVCM = –15V to 14.2V 100 dB
INPUT IMPEDANCE
Differential ✻107 || 2 Ω || pF
Common-Mode ✻109 || 4 Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL
R
L
= 100kΩ, V
O
= –14.75V to +14.75V
✻100 128 dB
TA = –40°C to +85°C
R
L
= 100kΩ, V
O
= –14.75V to +14.75V
100 dB
R
L
= 20kΩ, V
O
= –14.7V to +14.7V
✻100 128 dB
TA = –40°C to +85°C
R
L
= 20kΩ, V
O
= –14.7V to +14.7V
100 dB
FREQUENCY RESPONSE
Gain-Bandwidth Product GBW ✻35 kHz
Slew Rate SR G = 1 ✻0.01 V/µs
Overload Recovery Time VIN • G = VS✻60 µs
OUTPUT
Voltage Output Swing from Rail(2) VORL = 100kΩ, AOL ≥ 70dB ✻50 mV
RL = 100kΩ, AOL ≥ 100dB ✻75 250 mV
TA = –40°C to +85°CRL = 100kΩ, AOL ≥ 100dB 250 mV
RL = 20kΩ, AOL ≥ 100dB ✻100 300 mV
TA = –40°C to +85°CRL = 20kΩ, AOL ≥ 100dB 300 mV
Short-Circuit Current ISC
Single Versions ✻–21/+4 mA
Dual Versions ✻–50/+4 mA
Capacitive Load Drive CLOAD ✻See Typical Curve
POWER SUPPLY
Specified Voltage Range VS✻±15 V
Operating Voltage Range TA = –40°C to +85°C✻✻±1.35 ±18 V
Quiescent Current (per amplifier) IQIO = 0 ✻±27 ±38 µA
TA = –40°C to +85°CIO = 0 ±45 µA
TEMPERATURE RANGE
Specified Range ✻✻–40 +85 °C
Operating Range ✻✻–55 +125 °C
Storage Range ✻✻–55 +125 °C
Thermal Resistance
θ
JA
8-Pin DIP ✻100 °C/W
SO-8 Surface Mount ✻150 °C/W
14-Pin DIP ✻80 °C/W
SO-14 Surface Mount ✻100 °C/W
✻ Specifications the same as OPA251UA, PA.
NOTES: (1) The negative sign indicates input bias current flows out of the input terminals. (2) Output voltage swings are measured between the output and
power supply rails.
SPECIFICATIONS: VS = ±15V
At TA = +25°C, RL = 100kΩ connected to ground, unless otherwise noted.
Boldface limits apply over the specified temperature range, TA = –40°C to +85°C.
OPA241UA, PA OPA251UA, PA
OPA2241UA, PA OPA2251UA, PA
OPA4241UA, PA OPA4251UA, PA
4
®
OPA241, 2241, 4241
OPA251, 2251, 4251
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
ESD damage can range from subtle performance degrada-
tion to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.
Supply Voltage, V+ to V–.................................................................... 36V
Input Voltage(2) ..................................................(V–) –0.5V to (V+) +0.5V
Output Short Circuit to Ground(3) ............................................ Continuous
Operating Temperature ..................................................–55°C to +125°C
Storage Temperature .....................................................–55°C to +125°C
Junction Temperature...................................................................... 150°C
Lead Temperature (soldering, 10s)................................................. 300°C
NOTES: (1) Stresses above these ratings may cause permanent damage.
(2) Input terminals are diode-clamped to the power supply rails. Input signals
that can swing more that 0.5V beyond the supply rails should be current-
limited to 5mA or less. (3) One amplifier per package.
ABSOLUTE MAXIMUM RATINGS(1)
PACKAGE/ORDERING INFORMATION
OPERATING PACKAGE SPECIFICATION
SPECIFIED VOLTAGE DRAWING TEMPERATURE
PRODUCT VOLTAGE RANGE PACKAGE NUMBER(1) RANGE
OPA241 SERIES
Single
OPA241PA 2.7V to 5V 2.7V to 36V 8-Pin DIP 006 –40°C to +85°C
OPA241UA 2.7V to 5V 2.7V to 36V SO-8 Surface Mount 182 –40°C to +85°C
Dual
OPA2241PA 2.7V to 5V 2.7V to 36V 8-Pin DIP 006 –40°C to +85°C
OPA2241UA 2.7V to 5V 2.7V to 36V SO-8 Surface Mount 182 –40°C to +85°C
Quad
OPA4241PA 2.7V to 5V 2.7V to 36V 14-Pin DIP 010 –40°C to +85°C
OPA4241UA 2.7V to 5V 2.7V to 36V SO-14 Surface Mount 235 –40°C to +85°C
OPA251 SERIES
Single
OPA251PA ±15V 2.7V to 36V 8-Pin DIP 006 –40°C to +85°C
OPA251UA ±15V 2.7V to 36V SO-8 Surface Mount 182 –40°C to +85°C
Dual
OPA2251PA ±15V 2.7V to 36V 8-Pin DIP 006 –40°C to +85°C
OPA2251UA ±15V 2.7V to 36V SO-8 Surface Mount 182 –40°C to +85°C
Quad
OPA4251PA ±15V 2.7V to 36V 14-Pin DIP 010 –40°C to +85°C
OPA4251UA ±15V 2.7V to 36V SO-14 Surface Mount 235 –40°C to +85°C
NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book.
5
®
OPA241, 2241, 4241
OPA251, 2251, 4251
TYPICAL PERFORMANCE CURVES
At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted.
Curves apply to OPA241 and OPA251 unless specified.
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0.01 0.1
160
140
120
100
80
60
40
20
0
–20
Voltage Gain (dB)
180
160
140
120
100
80
60
40
20
0
Phase (°)
Frequency (Hz)
1 10 100 1k 10k 100k
Φ
G
V
S
= ±15V
V
S
= +5V
POWER SUPPLY and COMMON-MODE
REJECTION RATIO vs FREQUENCY
140
120
100
80
60
40
20
0
Power Supply Rejection Ratio (dB)
Frequency (Hz)
0.1 1 10 100 1k 10k 100k
–PSRR
+PSRR
CMRR
V
S
= ±15V
V
S
= ±5V
INPUT VOLTAGE AND CURRENT
NOISE SPECTRAL DENSITY vs FREQUENCY
1k
100
10
1k
100
10
Voltage Noise (nV/÷Hz)
Frequency (Hz)
0.1 1 10 100 1k 10k
Current Noise (fA/√Hz)
Current Noise
Voltage Noise
CHANNEL SEPARATION vs FREQUENCY
Frequency (Hz)
Channel Separation (dB)
140
130
120
110
100
90
80
70 10010 1k 10k 100k
Dual and quad devices.
G = 1, all channels.
Quad measured channel
A to D or B to C—other
combinations yield improved
rejection.
QUIESCENT CURRENT vs SUPPLY VOLTAGE
Total Supply Voltage (V)
Quiescent Current (µA)
30
28
26
24
22 0 5 10 15 20 25 30 35 40
Per Amplifier
QUIESCENT CURRENT vs TEMPERATURE
Temperature (°C)
Quiescent Current (µA)
40
35
30
25
20
15–75 –50 –25 0 25 50 75 100 125
V
S
= ±15V
V
S
= +5V
Per Amplifier
6
®
OPA241, 2241, 4241
OPA251, 2251, 4251
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted.
Curves apply to OPA241 and OPA251 unless specified.
INPUT BIAS CURRENT vs TEMPERATURE
Temperature (°C)
Input Bias Current (nA)
–6
–4
–2
0
2–75 –50 –25 0 25 50 75 100 125
I
B
I
OS
INPUT BIAS CURRENT
vs INPUT COMMON-MODE VOLTAGE
Common-Mode Voltage (V)
Input Bias Current (nA)
–5
–4
–3
–2
–1
00 5 10 15 20 25 30
I
B
I
OS
COMMON-MODE REJECTION vs TEMPERATURE
Temperature (°C)
Common-Mode Rejection (dB)
140
120
100
80
60
40
20
0–75 –50 –25 0 25 50 75 100 125
V
S
= ±15V
V
S
= +2.7V, +5V
V
CM
= (V–) –0.1V to (V+) –0.8V
V
CM
= (V–) –0.2V to (V+) –0.8V
V
CM
= (V–) to (V+) –0.8V
SHORT-CIRCUIT CURRENT vs TEMPERATURE
Temperature (°C)
Short-Circuit Current (mA)
50
45
40
35
30
25
20
15
10
5
0–75 –50 –25 0 25 50 75 100 125
–I
SC
+I
SC
, V
S
= +5V, ±15V (all versions)
V
S
= +5V
V
S
= ±15V
V
S
= +5V
V
S
= ±15V
Single Versions
Dual, Quad Versions
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
(V+)
(V+) –0.1V
(V+) –0.2V
(V+) –0.3V
(V–) +0.3V
(V–) +0.2V
(V–) +0.1V
(V–)0.1 ±1 ±10
Output Current (mA)
Output Voltage Swing (V)
T = +125°C
T = +25°C
T = –55°C
T = +125°C
T = +25°C, –55°C
OPEN-LOOP GAIN AND POWER
SUPPLY REJECTION vs TEMPERATURE
Temperature (°C)
A
OL
, PSR (dB)
140
130
120
110
100–75 –50 –25 0 25 50 75 100 125
R
L
= 20kΩ, 100kΩ
R
L
= 10kΩ
R
L
= 100kΩ
PSRR
A
OL
, V
S
= ±15V
A
OL
, V
S
= +5V
7
®
OPA241, 2241, 4241
OPA251, 2251, 4251
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted.
Curves apply to OPA241 and OPA251 unless specified.
OPA251 SERIES OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
Percent of Amplifiers (%)
Offset Voltage Drift (µV/°C)
18
16
14
12
10
8
6
4
2
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
Typical production distribution
of packaged units. Singles,
duals, and quads included.
V
S
= ±15V
OPA241 SERIES OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
Percent of Amplifiers (%)
Offset Voltage (µV)
30
25
20
15
10
5
0
V
S
= +5V
–225
–200
–175
–150
–125
–100
–75
–50
–25
0
25
50
75
100
125
150
175
200
225
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
OPA241 SERIES OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
Percent of Amplifiers (%)
Offset Voltage (µV/°C)
20
18
16
14
12
10
8
6
4
2
0
Typical production distribution
of packaged units. Singles,
duals, and quads included.
V
S
= +5V
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
OPA251 SERIES OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
Percent of Amplifiers (%)
Offset Voltage (µV)
30
25
20
15
10
5
0
V
S
= ±15V
–225
–200
–175
–150
–125
–100
–75
–50
–25
0
25
50
75
100
125
150
175
200
225
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100k100 1k 10k
Frequency (Hz)
10
30
25
20
15
10
5
0
Maximum Output Voltage (Vp-p)
Maximum output
voltage without
slew rate-induced
distortion.
VS = 2.7V
VS = +5V
VS = ±15V
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
140
130
120
110
100
90
80
Open-Loop Gain (dB)
Output Voltage Swing from Rail (mV)
500 400 300 200 100 0
V
S
= ±15V
V
S
= +5V
V
S
= +2.7V
R
L
= 20kΩR
L
= 100kΩ
R
L
= 10kΩ
8
®
OPA241, 2241, 4241
OPA251, 2251, 4251
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS ±15V), unless otherwise noted.
Curves apply to OPA241 and OPA251 unless specified.
0.5V/div
OPA241
SMALL-SIGNAL STEP RESPONSE
VS = +5V, G = +1, RL = 100kΩ, CL = 100pF
OPA241
LARGE-SIGNAL STEP RESPONSE
VS = +5V, G + 1, RL = 100kΩ, CL = 100pF
OPA251
SMALL-SIGNAL STEP RESPONSE
VS = ±15V, G = +1, RL = 100kΩ, CL = 500pF
OPA251
LARGE-SIGNAL STEP RESPONSE
VS = ±15V, G = +1, RL = 100kΩ, CL = 500pF
50mV/div
200µs/div 200µs/div
2V/div
50mV/div
200µs/div 2ms/div
QUIESCENT CURRENT
PRODUCTION DISTRIBUTION
Percent of Amplifiers (%)
Quiescent Current (µA)
35
30
25
20
15
10
5
0
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
V
S
= ±15V
Per Amplifier
Typical production distribution
of packaged units. Singles,
duals, and quads included.
QUIESCENT CURRENT
PRODUCT DISTRIBUTION
Percent of Amplifiers (%)
Quiescent Current (µA)
25
20
15
10
5
0
21
21.5
22
22.5
23
23.5
24
24.5
25
25.5
26
26.5
27
27.5
28
28.5
29
29.5
30
V
S
= +5V
Per Amplifier
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
9
®
OPA241, 2241, 4241
OPA251, 2251, 4251
APPLICATIONS INFORMATION
The OPA241 and OPA251 series are unity-gain stable and
suitable for a wide range of general purpose applications.
Power supply pins should be bypassed with 0.01µF ceramic
capacitors.
OPERATING VOLTAGE
The OPA241 series is laser-trimmed for low offset voltage
and drift at low supply voltage (VS = +5V). The OPA251
series is trimmed for ±15V operation. Both products operate
over the full voltage range (+2.7V to +36V or ±1.35V to
±18V) with some compromises in offset voltage and drift
performance. However, all other parameters have similar
performance. Key parameters are guaranteed over the speci-
fied temperature range, –40°C to +85°C. Most behavior
remains unchanged throughout the full operating voltage
range. Parameters which vary significantly with operating
voltage or temperature are shown in typical performance
curves.
OFFSET VOLTAGE TRIM
As mentioned previously, offset voltage of the OPA241
series is laser-trimmed at +5V. The OPA251 series is trimmed
at ±15V. Because the initial offset is so low, user adjustment
is usually not required. However, the OPA241 and OPA251
(single op amp versions) provide offset voltage trim connec-
tions on pins 1 and 5. Offset voltage can be adjusted by
connecting a potentiometer as shown in Figure 1. This
adjustment should be used only to null the offset of the op
amp, not to adjust system offset or offset produced by the
signal source. Nulling offset could degrade the offset drift
behavior of the op amp. While it is not possible to predict the
exact change in drift, the effect is usually small.
Figures 2 and 3 show the regions where the OPA241 series
and OPA251 series have the potential for instability. As
shown, the unity gain configuration with low supplies is the
most susceptible to the effects of capacitive load. With VS =
+5V, G = +1, and IOUT = 0, operation remains stable with
load capacitance up to approximately 200pF. Increasing
supply voltage, output current, and/or gain significantly
improves capacitive load drive. For example, increasing the
supplies to ±15V and gain to 10 allows approximately
2700pF to be driven.
One method of improving capacitive load drive in the unity
gain configuration is to insert a resistor inside the feedback
loop as shown in Figure 4. This reduces ringing with large
capacitive loads while maintaining dc accuracy. For ex-
ample, with VS = ±1.35V and RS = 5kΩ, the OPA241 series
and OPA251 series perform well with capacitive loads in
excess of 1000pF. Without the series resistor, capacitive
load drive is typically 200pF for these conditions. However,
this method will result in a slight reduction of output voltage
swing.
CAPACITIVE LOAD AND STABILITY
The OPA241 series and OPA251 series can drive a wide
range of capacitive loads. However, all op amps under
certain conditions may be unstable. Op amp configuration,
gain, and load value are just a few of the factors to consider
when determining stability.
V+
V–
100kΩ
Use offset adjust pins only to null
offset voltage of op amp—see text.
Trim Range: ±2mV
(V–) = 0V for single-supply operation.
OPA241 6
7
5
4
3
2
1
0.01µF
0.01µF
OPA241 and OPA251 (single op amps) only.
FIGURE 1. OPA241 and OPA251 Offset Voltage Trim
Circuit.
100k
10k
1k
100
Capacitive Load (pF)
Output Current (mA)
–1 –0.1 –0.01 0 0.01 0.1 1
Operation above
selected gain curve
not recommended
G = 10
G = –1
G = +1
Sinking Sourcing
V
S
= +2.7V
V
S
= +5V
FIGURE 2. Stability—Capacitive Load versus Output Cur-
rent for Low Supply Voltage.
FIGURE 3. Stability—Capacitive Load versus Output Cur-
rent for ±15V Supplies.
100k
10k
1k
100
Capacitive Load (pF)
Output Current (mA)
–1 –0.1 –0.01 0 0.01 0.1 1
Operation above
selected gain curve
not recommended
G = 10
G = –1
G = +1
V
S
= ±15V
Sinking Sourcing
10
®
OPA241, 2241, 4241
OPA251, 2251, 4251
R
L
10Ω
A1
OPA241
+
R
1
38.3kΩ
R
3
38.3kΩ
R
5
383kΩ
R
6
10kΩR
7
9.09kΩ
R
4
20kΩR
2
19.1kΩ
A2
OPA241
R
8
100kΩ
R
H
10Ω
I
H
V+
V–
V+
V–
2.7V to ±15V
V+ for A
1
, A
2
–In
+In
–In
+In V
O
= 10 • I
H
• R
H
To Load
To Load
V
O
= 10 • I
L
• R
L
Common-mode range of A2
extends to V– for low-side sensing.
Optional for I
B
Cancellation
(R
7
= R
6
II R
8
)
R
2
and R
4
divide down the
common-mode input to A1.
Low-Side
Current Sense
High-Side
Current Sense
Out
Out
NOTE: Low and high-side sensing circuits can be used independently.
V– for A
1
, A
2
I
L
FIGURE 5. Low and High-Side Battery Current Sensing.
R
S
5kΩ
OPA241
C
L
V
IN
V
OUT
FIGURE 4. Series Resistor in Unity Gain Configuration Improves Capacitive Load Drive.
