BB OPA4251UA

OPA241
®
OPA2241
OPA4241
OPA
241
OPA
425
OPA
1
OPA251
424
1
OPA
OPA2251
OPA4251
225
1
Single-Supply, MicroPOWER
OPERATIONAL AMPLIFIERS
OPA241 Family optimized for +5V supply.
DESCRIPTION
OPA251 Family optimized for ±15V supply.
The OPA241 series and OPA251 series are specifically
designed for battery powered, portable applications. In addition to very low power consumption (25µA), these amplifiers 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 products 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 provided 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.
FEATURES
●
●
●
●
●
●
●
●
MicroPOWER: 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
APPLICATIONS
● BATTERY OPERATED INSTRUMENTS
● PORTABLE DEVICES
● MEDICAL INSTRUMENTS
● TEST EQUIPMENT
OPA241, OPA251
Offset Trim
1
8
NC
Out A
1
–In
2
7
V+
–In A
2
+In
3
6
Output
+In A
3
V–
4
5
Offset Trim
V–
4
8-Pin DIP, SO-8
OPA4241, OPA4251
OPA2241, OPA2251
V+
Out A
1
14
Out D
7
Out B
–In A
2
13
–In D
6
–In B
+In A
3
12
+In D
5
+In B
V+
4
11
V–
+In B
5
10
+In C
8
A
B
8-Pin DIP, SO-8
A
B
D
C
–In B
6
9
–In C
Out B
7
8
Out C
14-Pin DIP, SO-14
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
© 1997 Burr-Brown Corporation
PDS-1406B
1
OPA241, 2241, 4241
Printed in U.S.A. October, 1998
OPA251, 2251,
4251
®
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.
OPA241UA, PA
OPA2241UA, PA
OPA4241UA, PA
PARAMETER
CONDITION
OFFSET VOLTAGE
Input Offset Voltage
TA = –40°C to +85°C
vs Temperature
vs Power Supply
TA = –40°C to +85°C
Channel Separation (dual, quad)
TA = –40°C to +85°C
VS = 2.7V to 36V
VS = 2.7V to 36V
dVOS/dT
PSRR
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current (per amplifier)
TA = –40°C to +85°C
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance
8-Pin DIP
SO-8 Surface Mount
14-Pin DIP
SO-14 Surface Mount
3
30
30
✻
±0.1
en
in
1
45
40
VCM
CMRR
VCM = –0.2V to (V+) –0.8V
VCM = 0V to (V+) –0.8V
–0.2
80
80
AOL
RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV
RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV
RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV
RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV
GBW
SR
VO
100
100
100
100
VS = 5V, G = 1
VIN • G = VS
RL = 100kΩ to VS /2, AOL ≥ 70dB
RL = 100kΩ to VS /2, AOL ≥ 100dB
RL = 100kΩ to VS /2, AOL ≥ 100dB
RL = 10kΩ to VS /2, AOL ≥ 100dB
RL = 10kΩ to VS /2, AOL ≥ 100dB
MAX
±100
±130
±0.6
IOS
TA = –40°C to +85°C
TA = –40°C to +85°C
Short-Circuit Current
Single Versions
Dual, Quad Versions
Capacitive Load Drive
±250
TYP(1)
±400
–4
TA = –40°C to +85°C
OUTPUT
Voltage Output Swing from Rail(3)
MIN
±100
±0.4
IB
INPUT IMPEDANCE
Differential
Common-Mode
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
Overload Recovery Time
MAX
✻
✻
✻
0.3
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz
Input Voltage Noise Density, f = 1kHz
Current Noise Density, f = 1kHz
OPEN-LOOP GAIN
Open-Loop Voltage Gain
TA = –40°C to +85°C
TYP(1)
±50
VOS
INPUT BIAS CURRENT
Input Bias Current(2)
TA = –40°C to +85°C
Input Offset Current
TA = –40°C to +85°C
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
TA = –40°C to +85°C
MIN
OPA251UA, PA
OPA2251UA, PA
OPA4251UA, PA
✻
–20
–25
±2
±2
UNITS
µV
µV
µV/°C
µV/V
µV/V
µV/V
nA
nA
nA
nA
✻
✻
✻
✻
µVp-p
nV/√Hz
fA/√Hz
106
✻
V
dB
dB
107 || 2
109 || 4
✻
✻
Ω || pF
Ω || pF
120
✻
120
✻
dB
dB
dB
dB
35
0.01
60
✻
✻
✻
kHz
V/µs
µs
✻
✻
mV
mV
mV
mV
mV
(V+) –0.8
50
75
100
100
100
200
200
✻
ISC
CLOAD
VS
IQ
✻
✻
✻
–24/+4
–30/+4
See Typical Curve
✻
+2.7 to +5
TA = –40°C to +85°C
IO = 0
IO = 0
+2.7
±25
–40
–55
–55
+36
±30
±36
✻
+85
+125
+125
✻
✻
✻
✻
✻
✻
✻
✻
θJA
100
150
80
100
mA
mA
✻
✻
✻
✻
V
V
µA
µA
°C
°C
°C
°C/W
°C/W
°C/W
°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.
®
OPA241, 2241, 4241
OPA251, 2251, 4251
2
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
OPA2241UA, PA
OPA4241UA, PA
PARAMETER
OFFSET VOLTAGE
Input Offset Voltage
TA = –40°C to +85°C
vs Temperature
vs Power Supply
TA = –40°C to +85°C
Channel Separation (dual, quad)
CONDITION
dVOS/dT
PSRR
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz
Input Voltage Noise Density, f = 1kHz
Current Noise Density, f = 1kHz
TA = –40°C to +85°C
VS = ±1.35V to ±18V
VS = ±1.35V to ±18V
OUTPUT
Voltage Output Swing from Rail(2)
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current (per amplifier)
TA = –40°C to +85°C
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance
8-Pin DIP
SO-8 Surface Mount
14-Pin DIP
SO-14 Surface Mount
TYP
±50
✻
✻
✻
±0.1
en
in
✻
✻
✻
1
45
40
(V–) –0.2
100
100
✻
✻
AOL
GBW
SR
VO
✻
RL = 100kΩ, VO = –14.75V to +14.75V
RL = 100kΩ, VO = –14.75V to +14.75V
RL = 20kΩ, VO = –14.7V to +14.7V
RL = 20kΩ, VO = –14.7V to +14.7V
100
100
100
100
✻
G=1
VIN • G = VS
RL = 100kΩ, AOL ≥ 70dB
RL = 100kΩ, AOL ≥ 100dB
RL = 100kΩ, AOL ≥ 100dB
RL = 20kΩ, AOL ≥ 100dB
RL = 20kΩ, AOL ≥ 100dB
µV
µV
µV/°C
µV/V
µV/V
µV/V
30
30
IOS
✻
±250
3
–4
VCM = –15.2V to 14.2V
VCM = –15V to 14.2V
UNITS
±300
✻
VCM
CMRR
MAX
±100
±0.5
IB
TA = –40°C to +85°C
TA = –40°C to +85°C
Short-Circuit Current
Single Versions
Dual Versions
Capacitive Load Drive
MIN
0.3
TA = –40°C to +85°C
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
Overload Recovery Time
MAX
✻
INPUT IMPEDANCE
Differential
Common-Mode
OPEN-LOOP GAIN
Open-Loop Voltage Gain
TA = –40°C to +85°C
TYP
±100
±150
±0.6
✻
VOS
INPUT BIAS CURRENT
Input Bias Current(1)
TA = –40°C to +85°C
Input Offset Current
TA = –40°C to +85°C
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
TA = –40°C to +85°C
MIN
OPA251UA, PA
OPA2251UA, PA
OPA4251UA, PA
–20
–25
±2
±2
nA
nA
nA
nA
µVp-p
nV/√Hz
fA/√Hz
124
(V+) –0.8
V
dB
dB
107 || 2
109 || 4
Ω || pF
Ω || pF
128
dB
dB
dB
dB
128
✻
✻
✻
35
0.01
60
✻
✻
50
75
✻
100
✻
✻
✻
–21/+4
–50/+4
See Typical Curve
mA
mA
±15
±45
±38
V
V
µA
µA
+85
+125
+125
°C
°C
°C
kHz
V/µs
µs
250
250
300
300
mV
mV
mV
mV
mV
ISC
CLOAD
VS
IQ
TA = –40°C to +85°C
IO = 0
IO = 0
✻
✻
✻
±1.35
✻
✻
✻
✻
✻
✻
✻
±27
–40
–55
–55
θJA
✻
✻
✻
✻
100
150
80
100
±18
°C/W
°C/W
°C/W
°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.
3
OPA241, 2241, 4241
OPA251, 2251, 4251
®
ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
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
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.
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 currentlimited to 5mA or less. (3) One amplifier per package.
ESD damage can range from subtle performance degradation 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.
PACKAGE/ORDERING INFORMATION
SPECIFIED
VOLTAGE
OPERATING
VOLTAGE
RANGE
PACKAGE
PACKAGE
DRAWING
NUMBER(1)
SPECIFICATION
TEMPERATURE
RANGE
Single
OPA241PA
OPA241UA
2.7V to 5V
2.7V to 5V
2.7V to 36V
2.7V to 36V
8-Pin DIP
SO-8 Surface Mount
006
182
–40°C to +85°C
–40°C to +85°C
Dual
OPA2241PA
OPA2241UA
2.7V to 5V
2.7V to 5V
2.7V to 36V
2.7V to 36V
8-Pin DIP
SO-8 Surface Mount
006
182
–40°C to +85°C
–40°C to +85°C
Quad
OPA4241PA
OPA4241UA
2.7V to 5V
2.7V to 5V
2.7V to 36V
2.7V to 36V
14-Pin DIP
SO-14 Surface Mount
010
235
–40°C to +85°C
–40°C to +85°C
Single
OPA251PA
OPA251UA
±15V
±15V
2.7V to 36V
2.7V to 36V
8-Pin DIP
SO-8 Surface Mount
006
182
–40°C to +85°C
–40°C to +85°C
Dual
OPA2251PA
OPA2251UA
±15V
±15V
2.7V to 36V
2.7V to 36V
8-Pin DIP
SO-8 Surface Mount
006
182
–40°C to +85°C
–40°C to +85°C
Quad
OPA4251PA
OPA4251UA
±15V
±15V
2.7V to 36V
2.7V to 36V
14-Pin DIP
SO-14 Surface Mount
010
235
–40°C to +85°C
–40°C to +85°C
PRODUCT
OPA241 SERIES
OPA251 SERIES
NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book.
®
OPA241, 2241, 4241
OPA251, 2251, 4251
4
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.
POWER SUPPLY and COMMON-MODE
REJECTION RATIO vs FREQUENCY
180
140
160
120
140
G
100
120
80
Φ
100
60
80
40
60
20
40
VS = ±15V
VS = +5V
0
–20
0.01
0.1
140
20
1
10
100
1k
10k
Power Supply Rejection Ratio (dB)
160
Phase (°)
Voltage Gain (dB)
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0
100k
VS = ±15V
VS = ±5V
120
CMRR
100
80
+PSRR
60
–PSRR
40
20
0
0.1
1
10
100
1k
10k
Frequency (Hz)
Frequency (Hz)
CHANNEL SEPARATION vs FREQUENCY
INPUT VOLTAGE AND CURRENT
NOISE SPECTRAL DENSITY vs FREQUENCY
140
100k
1k
1k
120
110
Dual and quad devices.
G = 1, all channels.
Quad measured channel
A to D or B to C—other
combinations yield improved
rejection.
100
90
80
70
Current Noise
100
Voltage Noise
10
10
100
1k
10k
10
0.1
100k
1
10
Frequency (Hz)
100
1k
10k
Frequency (Hz)
QUIESCENT CURRENT vs SUPPLY VOLTAGE
QUIESCENT CURRENT vs TEMPERATURE
30
40
Per Amplifier
Per Amplifier
Quiescent Current (µA)
Quiescent Current (µA)
100
28
26
24
22
35
VS = ±15V
30
25
VS = +5V
20
15
0
5
10
15
20
25
30
35
40
–75
Total Supply Voltage (V)
–50
–25
0
25
50
75
100
125
Temperature (°C)
5
OPA241, 2241, 4241
OPA251, 2251, 4251
®
Current Noise (fA/√Hz)
Voltage Noise (nV/÷Hz)
Channel Separation (dB)
130
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 INPUT COMMON-MODE VOLTAGE
INPUT BIAS CURRENT vs TEMPERATURE
–5
–6
Input Bias Current (nA)
Input Bias Current (nA)
IB
–4
IB
–2
IOS
0
–4
–3
–2
–1
IOS
0
2
0
–75
–50
–25
0
25
50
75
100
5
10
125
15
20
25
30
Common-Mode Voltage (V)
Temperature (°C)
COMMON-MODE REJECTION vs TEMPERATURE
SHORT-CIRCUIT CURRENT vs TEMPERATURE
50
140
Short-Circuit Current (mA)
Common-Mode Rejection (dB)
VS = ±15V
45
–ISC
40
VS = +5V
35
30
25
VS = +5V
20
Single Versions
Dual, Quad Versions
15
10
VS = ±15V
+ISC, VS = +5V, ±15V (all versions)
5
VS = ±15V
120
VS = +2.7V, +5V
100
80
60
40
VCM = (V–) –0.2V to (V+) –0.8V
VCM = (V–) –0.1V to (V+) –0.8V
VCM = (V–) to (V+) –0.8V
20
0
0
–75
–50
–25
0
25
50
75
100
–75
125
–50
–25
Temperature (°C)
0
25
50
75
100
125
Temperature (°C)
OPEN-LOOP GAIN AND POWER
SUPPLY REJECTION vs TEMPERATURE
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
(V+)
140
T = +25°C
RL = 20kΩ, 100kΩ
AOL, PSR (dB)
130
RL = 100kΩ
120
RL = 10kΩ
110
AOL, VS = ±15V
AOL, VS = +5V
Output Voltage Swing (V)
(V+) –0.1V
T = –55°C
T = +125°C
(V+) –0.2V
(V+) –0.3V
(V–) +0.3V
T = +125°C
(V–) +0.2V
T = +25°C, –55°C
(V–) +0.1V
PSRR
(V–)
100
–75
–50
–25
0
25
50
75
100
0.1
125
®
OPA241, 2241, 4241
OPA251, 2251, 4251
±1
Output Current (mA)
Temperature (°C)
6
±10
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.
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
140
30
Open-Loop Gain (dB)
Maximum Output Voltage (Vp-p)
RL = 20kΩ
VS = ±15V
RL = 100kΩ
130
VS = +5V
120
VS = +2.7V
110
RL = 10kΩ
100
90
80
400
10
VS = +5V
5
VS = 2.7V
300
200
100
0
100
1k
10k
Output Voltage Swing from Rail (mV)
Frequency (Hz)
OPA241 SERIES OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
OPA241 SERIES OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
100k
20
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
VS = +5V
VS = +5V
18
Percent of Amplifiers (%)
Percent of Amplifiers (%)
20
15
10
30
25
20
0
500
Maximum output
voltage without
slew rate-induced
distortion.
VS = ±15V
25
15
10
5
Typical production distribution
of packaged units. Singles,
duals, and quads included.
16
14
12
10
8
6
4
2
0
–225
–200
–175
–150
–125
–100
–75
–50
–25
0
25
50
75
100
125
150
175
200
225
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
Offset Voltage (µV/°C)
Offset Voltage (µV)
OPA251 SERIES OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
OPA251 SERIES OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
30
18
20
16
15
10
5
14
VS = ±15V
Typical production distribution
of packaged units. Singles,
duals, and quads included.
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
0
–225
–200
–175
–150
–125
–100
–75
–50
–25
0
25
50
75
100
125
150
175
200
225
Percent of Amplifiers (%)
25
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
Percent of Amplifiers (%)
VS = ±15V
Offset Voltage (µV)
Offset Voltage Drift (µV/°C)
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.
QUIESCENT CURRENT
PRODUCT DISTRIBUTION
QUIESCENT CURRENT
PRODUCTION DISTRIBUTION
25
35
Typical production
distribution of
packaged units.
Singles, duals,
and quads included.
Per Amplifier
Percent of Amplifiers (%)
20
VS = ±15V
Typical production distribution
of packaged units. Singles,
duals, and quads included.
30
15
10
5
25
20
15
10
Per Amplifier
5
0
Quiescent Current (µA)
Quiescent Current (µA)
OPA241
SMALL-SIGNAL STEP RESPONSE
VS = +5V, G = +1, RL = 100kΩ, CL = 100pF
0.5V/div
50mV/div
OPA241
LARGE-SIGNAL STEP RESPONSE
VS = +5V, G + 1, RL = 100kΩ, CL = 100pF
200µs/div
200µs/div
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
2V/div
2ms/div
200µs/div
®
OPA241, 2241, 4241
OPA251, 2251, 4251
8
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
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
0
50mV/div
Percent of Amplifiers (%)
VS = +5V
APPLICATIONS INFORMATION
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 example, 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.
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 specified 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 connections 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.
V+
100k
Capacitive Load (pF)
VS = +2.7V
VS = +5V
Operation above
selected gain curve
not recommended
10k
G = 10
1k
G = –1
Sinking
Sourcing
G = +1
100
–1
–0.1
–0.01
0
0.01
0.1
1
Output Current (mA)
FIGURE 2. Stability—Capacitive Load versus Output Current for Low Supply Voltage.
OPA241 and OPA251 (single op amps) only.
0.01µF
Use offset adjust pins only to null
offset voltage of op amp—see text.
7
2
6
3
OPA241
100k
5
VS = ±15V
1
100kΩ
Capacitive Load (pF)
0.01µF 4
Operation above
selected gain curve
not recommended
Trim Range: ±2mV
(V–) = 0V for single-supply operation.
V–
FIGURE 1. OPA241 and OPA251 Offset Voltage Trim
Circuit.
10k
G = 10
G = –1
1k
G = +1
Sinking
Sourcing
100
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.
–1
–0.1
–0.01
0
0.01
0.1
1
Output Current (mA)
FIGURE 3. Stability—Capacitive Load versus Output Current for ±15V Supplies.
9
OPA241, 2241, 4241
OPA251, 2251, 4251
®
RS
5kΩ
OPA241
VOUT
VIN
CL
FIGURE 4. Series Resistor in Unity Gain Configuration Improves Capacitive Load Drive.
RH
10Ω
To Load
R5
383kΩ
IH
High-Side
Current Sense
R3
38.3kΩ
R1
38.3kΩ
V+
–In
A1
+In OPA241
V+ for A1, A2
R4
20kΩ
R2
19.1kΩ
Out
VO = 10 • IH • RH
V–
+
2.7V to ±15V
R2 and R4 divide down the
common-mode input to A1.
R8
100kΩ
V– for A1, A2
V+
–In
A2
+In OPA241
V–
R7
9.09kΩ
R6
10kΩ
RL
10Ω
Out
VO = 10 • IL • RL
Low-Side
Current Sense
Common-mode range of A2
extends to V– for low-side sensing.
Optional for IB Cancellation
(R7 = R6 II R8)
To Load
IL
NOTE: Low and high-side sensing circuits can be used independently.
FIGURE 5. Low and High-Side Battery Current Sensing.
®
OPA241, 2241, 4241
OPA251, 2251, 4251
10