BB OPA357AIDBVR

OPA357
OPA2357
SBOS235C − MARCH 2002− REVISED MAY 2004
250MHz, Rail-to-Rail I/O, CMOS
Operational Amplifier with Shutdown
FEATURES
DESCRIPTION
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The OPA357 series of high-speed, voltage-feedback
CMOS operational amplifiers are designed for video and
other applications requiring wide bandwidth. They are
unity-gain stable and can drive large output currents.
Differential gain is 0.02% and differential phase is 0.09°.
Quiescent current is only 4.9mA per channel.
The OPA357 series op amps are optimized for operation
on single or dual supplies as low as 2.5V (±1.25V) and up
to 5.5V (±2.75V). Common-mode input range extends
beyond the supplies. The output swing is within 100mV of
the rails, supporting wide dynamic range.
For applications requiring the full 100mA continuous
output current, the single SO-8 PowerPAD version is
available.
The single version (OPA357), comes in the miniature
SOT23-6 and SO-8 PowerPAD packages. The dual
version (OPA2357) is offered in the MSOP-10 package.
The dual version features completely independent
circuitry for lowest crosstalk and freedom from interaction.
All are specified over the extended −40°C to +125°C
temperature range.
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UNITY-GAIN BANDWIDTH: 250MHz
WIDE BANDWIDTH: 100MHz GBW
HIGH SLEW RATE: 150V/ms
LOW NOISE: 6.5nV/√Hz
RAIL-TO-RAIL I/O
HIGH OUTPUT CURRENT: > 100mA
EXCELLENT VIDEO PERFORMANCE:
Diff Gain: 0.02%, Diff Phase: 0.095
0.1dB Gain Flatness: 40MHz
LOW INPUT BIAS CURRENT: 3pA
QUIESCENT CURRENT: 4.9mA
THERMAL SHUTDOWN
SUPPLY RANGE: 2.5V to 5.5V
SHUTDOWN IQ < 6mA
MicroSIZE AND PowerPAD PACKAGES
APPLICATIONS
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VIDEO PROCESSING
ULTRASOUND
OPTICAL NETWORKING, TUNABLE LASERS
PHOTODIODE TRANSIMPEDANCE AMPS
ACTIVE FILTERS
HIGH-SPEED INTEGRATORS
ANALOG-TO-DIGITAL (A/D) CONVERTER
INPUT BUFFERS
DIGITAL-TO-ANALOG (D/A) CONVERTER
OUTPUT AMPLIFIERS
BARCODE SCANNERS
COMMUNICATIONS
OPAx357 RELATED PRODUCTS
FEATURES
PRODUCT
Non-Shutdown Version of OPA357 Family
OPAx354
200MHz GBW, Rail-to-Rail Output, CMOS, Shutdown
OPAx355
200MHz GBW, Rail-to-Rail Output, CMOS
OPAx356
38MHz GBW, Rail-to-Rail Input/Output, CMOS
OPAx350/3
75MHz BW G = 2, Rail-to-Rail Output
OPAx631
150MHz BW G = 2, Rail-to-Rail Output
OPAx634
100MHz BW, Differential Input/Output, 3.3V Supply
THS412x
V+
−VIN
VOUT
OPA357
+VIN
V−
Enable
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
Copyright  2002-2004, Texas Instruments Incorporated
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SBOS235C − MARCH 2002− REVISED MAY 2004
ELECTROSTATIC
DISCHARGE SENSITIVITY
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage, V+ to V− . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5V
Signal Input Terminals Voltage(2) . . . (V−) − (0.5V) to (V+) + (0.5V)
Current(2) . . . . . . . . . . . . . . . . . . . . . 10mA
This integrated circuit can be damaged by ESD. Texas Instruments
recommends that all integrated circuits be handled with appropriate
precautions. Failure to observe proper handling and installation
procedures can cause damage.
Enable Input . . . . . . . . . . . . . . . . . . . . (V−) − (0.5V) to (V+) + (0.5V)
Output Short-Circuit(3) . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . −55°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . −65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . . +300°C
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.
(1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not supported.
(2) Input terminals are diode-clamped to the power-supply rails.
Input signals that can swing more than 0.5V beyond the supply
rails should be current limited to 10mA or less.
(3) Short-circuit to ground, one amplifier per package.
PACKAGE/ORDERING INFORMATION(1)
PRODUCT
PACKAGE−LEAD
PACKAGE
DESIGNATOR(1)
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
OPA357
SO-8 PowerPAD
DDA
−40°C to +125°C
OPA357A
OPA357AIDDA
OPA357AIDDAR
Rails, 97
Tape and Reel, 2500
OPA357
SOT23-6
DBV
−40°C to +125°C
OADI
OPA357AIDBVT
OPA357AIDBVR
Tape and Reel, 250
Tape and Reel, 3000
OPA2357
MSOP-10
DGS
−40°C to +125°C
BBG
OPA2357AIDGST
OPA2357AIDGSR
Tape and Reel, 250
Tape and Reel, 2500
″
″
″
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″
″
″
″
″
″
″
″
″
″
″
(1) For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet.
PIN CONFIGURATION
Top View
OPA357
1
V−
2
+In
OADI
Out
3
OPA357
6
V+
5
Enable
OPA2357
NC (2 )
1
8
Enable
Out A
1
−In
2
7
V+
−In A
2
10 V+
9
Out B
8
−In B
A
4
−In
+In
3
6
Out
+In A
3
B
V−
4
5
NC (2 )
V−
4
7
+In B
Enable A
5
6
Enable B
SOT23(1)
SO PowerPAD(3)
MSOP−10
NOTES: (1) Pin 1 of the SOT23-6 is determined by orienting the package marking as indicated in the diagram.
(2) NC means no internal connection.
(3) PowerPAD should be connected to V− or left floating.
2
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SBOS235C − MARCH 2002− REVISED MAY 2004
ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V Single-Supply
Boldface limits apply over the temperature range, TA = −40°C to +125°C.
All specifications at TA = +25°C, RF = 0Ω , RL = 1kΩ connected to VS/2, unless otherwise noted.
OPA357AI
OPA2357AI
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
OFFSET VOLTAGE
Input Offset Voltage
VOS
vs Temperature
dVOS/dT
vs Power Supply
PSRR
±2
VS = +5V
Specified Temperature Range
Specified Temperature Range
+4
VS = +2.7V to +5.5V, VCM = (VS/2) − 0.15V
Specified Temperature Range
±200
±8
mV
+10
mV
µV/°C
±800
µV/V
±900
µV/V
3
±50
pA
±1
±50
pA
INPUT BIAS CURRENT
Input Bias Current
Input Offset Current
IB
IOS
NOISE
Input Voltage Noise Density
Current Noise Density
en
in
f = 1MHz
6.5
nV/√Hz
f = 1MHz
50
fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
VCM
CMRR
(V−) − (0.1)
VS = +5.5V, −0.1V < VCM < +3.5V
Specified Temperature Range
66
VS = +5.5V, −0.1V < VCM < +5.6V
Specified Temperature Range
56
(V+) + (0.1V)
80
V
dB
64
dB
68
dB
55
dB
INPUT IMPEDANCE
1013 || 2
1013 || 2
Differential
Common-Mode
OPEN-LOOP GAIN
AOL
Specified Temperature Range
VS = +5V, +0.3V < VO < +4.7V
VS = +5V, +0.4V < VO < +4.6V
94
Ω || pF
Ω || pF
110
dB
90
dB
FREQUENCY RESPONSE
Small-Signal Bandwidth
f−3dB
f−3dB
G = +1, VO = 100mVPP, RF = 25Ω
250
MHz
G = +2, VO = 100mVPP
90
MHz
GBW
G = +10
100
MHz
f0.1dB
SR
G = +2, VO = 100mVPP
40
MHz
VS = +5V, G = +1, 4V Step
VS = +5V, G = +1, 2V Step
150
V/µs
130
V/µs
VS = +3V, G = +1, 2V Step
G = +1, VO = 200mVPP, 10% to 90%
110
V/µs
2
ns
G = 1, VO = 2VPP, 10% to 90%
11
ns
VS = +5V, G = +1, 2V Output Step
30
ns
60
ns
VIN S Gain = VS
5
ns
2nd-Harmonic
G = +1, f = 1MHz, VO = 2VPP, RL = 200Ω, VCM = 1.5V
−75
dBc
3rd-Harmonic
G = +1, f = 1MHz, VO = 2VPP, RL = 200Ω, VCM = 1.5V
−83
dBc
Differential Gain Error
NTSC, RL = 150Ω
0.02
%
Differential Phase Error
NTSC, RL = 150Ω
0.09
degrees
f = 5MHz
−100
dB
VS = +5V, RL = 1kΩ, AOL > 94dB
VS = +5V, RL = 1kΩ, AOL > 90dB
VS = +5V
0.1
Gain-Bandwidth Product
Bandwidth for 0.1dB Gain Flatness
Slew Rate
Rise-and-Fall Time
Settling Time, 0.1%
0.01%
Overload Recovery Time
Harmonic Distortion
Channel-to-Channel Crosstalk, OPA2357
OUTPUT
Voltage Output Swing from Rail
Specified Temperature Range
Output Current(1)(2), Single, Dual
IO
VS = +3V
f < 100kHz
Closed-Loop Output Impedance
Open-Loop Output Resistance
RO
0.3
0.4
100
V
V
mA
50
mV
0.05
Ω
35
Ω
(1) See typical characteristics Output Voltage Swing vs Output Current.
(2) Specified by design.
3
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SBOS235C − MARCH 2002− REVISED MAY 2004
ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V Single-Supply (continued)
Boldface limits apply over the temperature range, TA = −40°C to +125°C.
All specifications at TA = +25°C, RF = 0Ω , RL = 1kΩ connected to VS/2, unless otherwise noted.
OPA357AI
OPA2357AI
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
6
mA
7.5
mA
0.8
V
POWER SUPPLY
Specified Voltage Range
VS
2.7
Operating Voltage Range
Quiescent Current (per amplifier)
2.5 to 5.5
IQ
VS = +5V, Enabled, IO = 0
Specified Temperature Range
4.9
V
ENABLE/SHUTDOWN FUNCTION
Disabled (logic−LOW Threshold)
Enabled (logic−HIGH Threshold)
2
Logic Input Current
Logic LOW
V
200
nA
Turn-On Time
100
ns
Turn-Off Time
30
ns
74
dB
Off Isolation
G = +1, 5MHz, RL = 10Ω
Quiescent Current (per amplifier)
3.4
6
µA
THERMAL SHUTDOWN
Junction Temperature
TJ
Shutdown
+160
°C
Reset from Shutdown
+140
°C
TEMPERATURE RANGE
Specified Range
−40
+125
°C
Operating Range
−55
+150
°C
Storage Range
−65
+150
Thermal Resistance
qJA
SOT23-6
150
°C/W
SO-8 PowerPAD
65
°C/W
MSOP-10
150
°C/W
(1) See typical characteristics Output Voltage Swing vs Output Current.
(2) Specified by design.
4
°C
°C/W
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SBOS235C − MARCH 2002− REVISED MAY 2004
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
INVERTING SMALL−SIGNAL
FREQUENCY RESPONSE
NONINVERTING SMALL−SIGNAL
FREQUENCY RESPONSE
3
VO = 0.1VPP, RF = 604Ω
0
Normalized Gain (dB)
0
Normalized Gain (dB)
3
G = +1
RF = 25Ω
VO = 0.1VPP
G = +2, RF = 604Ω
−3
G = +5, RF = 604Ω
−6
G = +10, RF = 604Ω
−9
−3
G = −1
−6
G = −5
G = −2
−9
G = −10
−12
−12
−15
100k
1M
10M
Frequency (Hz)
100M
−15
100k
1G
10M
Frequency (Hz)
100M
1G
NONINVERTING LARGE−SIGNAL STEP RESPONSE
Output Voltage (40mV/div)
Output Voltage (500mV/div)
NONINVERTING SMALL−SIGNAL STEP RESPONSE
1M
Time (20ns/div)
Time (20ns/div)
0.1dB GAIN FLATNESS
0.5
LARGE−SIGNAL DISABLE/ENABLE RESPONSE
4.5
3.5
2.5
1.5
0.5
Disabled
Normalized Gain (dB)
Enabled
Disable Voltage (V)
Output Voltage (400mV/div)
0.4
VO = 0.1VPP
0.3
G = +1
RF = 25Ω
0.2
0.1
0
−0.1
−0.2
G = +2
RF = 604Ω
−0.3
−0.4
VOUT
fIN = 5MHz
−0.5
100k
Time (200ns/div)
1M
10M
Frequency (Hz)
100M
1G
5
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SBOS235C − MARCH 2002− REVISED MAY 2004
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
HARMONIC DISTORTION vs OUTPUT VOLTAGE
HARMONIC DISTORTION vs NONINVERTING GAIN
−50
G = −1
f = 1MHz
RL = 200Ω
−60
−70
2nd−Harmonic
−80
−90
0
1
2
Output Voltage (VPP)
3
−70
2nd−Harmonic
−80
−90
3rd−Harmonic
3rd−Harmonic
−100
VO = 2VPP
f = 1MHz
RL = 200Ω
−60
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
−50
−100
4
1
10
Gain (V/V)
HARMONIC DISTORTION vs INVERTING GAIN
HARMONIC DISTORTION vs FREQUENCY
−50
VO = 2VPP
f = 1MHz
R L = 200Ω
−60
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
−50
−70
2nd−Harmonic
−80
−90
−60
G = +1
VO = 2VPP
RL = 200Ω
VCM = 1.5V
−70
2nd−Harmonic
−80
3rd−Harmonic
−90
3rd−Harmonic
−100
1
10
−100
100k
1M
Frequency (Hz)
Gain (V/V)
INPUT VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
HARMONIC DISTORTION vs LOAD RESISTANCE
−60
10k
G = +1
VO = 2VPP
f = 1MHz
VCM = 1.5V
−70
Voltage Noise (nV/√Hz),
Current Noise (fA/√Hz)
Harmonic Distortion (dBc)
−50
2nd−Harmonic
−80
3rd−Harmonic
−90
−100
1k
Voltage Noise
Current Noise
100
10
1
100
1k
RL (Ω)
6
10M
10
100
1k
10k
100k
Frequency (Hz)
1M
10M
100M
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
FREQUENCY RESPONSE FOR VARIOUS RL
FREQUENCY RESPONSE FOR VARIOUS CL
3
9
RL = 10kΩ
−3
−6
Normalized Gain (dB)
Normalized Gain (dB)
0
G = +1
RF = 0Ω
VO = 0.1VPP
CL = 0pF
G = +1
VO = 0.1VPP
RS = 0Ω
6
RL = 1kΩ
RL = 100Ω
−9
RL = 50Ω
3
0
−3
CL = 47pF
−6
−9
−12
CL = 5.6pF
−12
−15
100k
1M
10M
Frequency (Hz)
100M
−15
100k
1G
RECOMMENDED RS vs CAPACITIVE LOAD
1M
10M
Frequency (Hz)
100M
1G
FREQUENCY RESPONSE vs CAPACITIVE LOAD
160
3
For 0.1dB
Flatness
G = +1,
VO = 0.1VPP
0
Normalized Gain (dB)
140
120
100
RS (Ω)
CL = 100pF
80
60
VIN
40
RS
VO
OPA357
CL
0
1k
10
100
Capacitive Load (pF)
CL = 47pF, RS = 140 Ω
−3
CL = 100pF, RS = 120Ω
−6
−9
VIN
RS
VO
OPA357
−12
1kΩ
20
1
CL = 5.6pF, RS = 0Ω
CL
−15
100k
1M
COMMON−MODE REJECTION RATIO AND
POWER−SUPPLY REJECTION RATIO vs FREQUENCY
1kΩ
10M
Frequency (Hz)
1G
100M
OPEN−LOOP GAIN AND PHASE
180
100
160
Open−Loop Phase (degrees)
Open−Loop Gain (dB)
CMRR
CMRR, PSRR (dB)
80
PSRR+
60
PSRR−
40
20
140
120
Phase
100
80
60
40
Gain
20
0
−20
−40
0
10k
100k
1M
10M
Frequency (Hz)
100M
1G
10
100
1k
10k 100k
1M
Frequency (Hz)
10M
100M
1G
7
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SBOS235C − MARCH 2002− REVISED MAY 2004
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
COMPOSITE VIDEO
DIFFERENTIAL GAIN AND PHASE
INPUT BIAS CURRENT vs TEMPERATURE
10k
0.8
Input Bias Current (pA)
dG/dP (%/degrees)
0.7
0.6
0.5
dP
0.4
0.3
0.2
0.1
1k
100
10
dG
1
0
1
2
3
−55
4
−35
−15
5
Number of 150Ω Loads
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
FOR VS = 3V
25
45
65
Temperature (_C)
85
105 125 135
SUPPLY CURRENT vs TEMPERATURE
7
3
Supply Current (mA)
Output Voltage (V)
6
2
+125_ C
+25_ C
−55_ C
1
VS = 5V
5
4
VS = 2.5V
3
2
1
0
0
0
20
40
60
80
100
−55
120
−35
−15
5
Output Current (mA)
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
FOR VS = 5V
105 125 135
SHUTDOWN CURRENT vs TEMPERATURE
VS = 5.5V
4
Shutdown Current (µA)
4
Output Voltage (V)
85
4.5
5
3
−55_C
+25_ C
+125_ C
2
1
3.5
3
VS = 5V
2.5
2
1.5
1
0
VS = 2.5V
VS = 3V
0.5
0
0
25
50
75
100
125
Output Current (mA)
8
25
45
65
Temperature (_ C)
150
175
200
−55
−35
−15
5
25
45
65
Temperature (_C)
85
105
125 135
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
CLOSED−LOOP OUTPUT IMPEDANCE vs FREQUENCY
DISABLE FEEDTHROUGH vs FREQUENCY
0
Output Impedance (Ω)
VDISABLE = 0
RL = 10Ω
−20
Feedthrough (dB)
100
−40
−60
Forward
Reverse
−80
10
1
0.1
OPA357
−100
ZO
−120
100k
1M
10M
Frequency (Hz)
100M
0.01
100k
1G
1M
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100M
1G
OUTPUT SETTLING TIME TO 0.1%
6
0.5
VS = 5.5V
0.4
5
4
VO = 2VPP
0.3
Maximum Output
Voltage without
Slew−Rate
Induced Distortion
Output Error (%)
Output Voltage (VPP)
10M
Frequency (Hz)
3
VS = 2.7V
2
0.2
0.1
0
−0.1
−0.2
−0.3
1
−0.4
−0.5
0
1
10
Frequency (MHz)
0
100
10
20
30
40
50
60
70
80
90
100
Time (ns)
OPEN−LOOP GAIN vs TEMPERATURE
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
120
Population
Open−Loop Gain (dB)
RL = 1kΩ
110
100
90
80
70
−55
−35
−15
5
25
45
65
Temperature (_ C)
85
105 125 135
−8 −7 −6 −5 −4 −3 −2 −1 0 1 2 3
Offset Voltage (mV)
4 5 6
7 8
9
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SBOS235C − MARCH 2002− REVISED MAY 2004
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted.
COMMON−MODE REJECTION RATIO AND
POWER−SUPPLY REJECTION RATIO vs TEMPERATURE
CHANNEL−TO−CHANNEL CROSSTALK
0
Crosstalk, Input−Referred (dB)
100
CMRR, PSRR (dB)
90
Common−Mode Rejection Ratio
80
Power−Supply Rejection Ratio
70
60
50
−55
−35
−15
5
25
45
65
Temperature (_ C)
10
85
105 125 135
−20
−40
−60
OPA2357
−80
−100
−120
100k
1M
10M
Frequency (Hz)
100M
1G
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APPLICATIONS INFORMATION
The OPA357 is a CMOS, rail-to-rail I/O, high-speed,
voltage-feedback operational amplifier designed for video,
high-speed, and other applications. It is available as a
single or dual op amp.
The amplifier features a 100MHz gain bandwidth, and
150V/µs slew rate, but it is unity-gain stable and can be
operated as a +1V/V voltage follower.
OPERATING VOLTAGE
The OPA357 is specified over a power-supply range of
+2.7V to +5.5V (±1.35V to ±2.75V). However, the supply
voltage may range from +2.5V to +5.5V (±1.25V to
±2.75V). Supply voltages higher than 7.5V (absolute
maximum) can permanently damage the amplifier.
Parameters that vary over supply voltage or temperature
are shown in the Typical Characteristics section of this
data sheet.
ENABLE FUNCTION
The OPA357’s Enable function is implemented using a
Schmitt trigger. The amplifier is enabled by applying a TTL
HIGH voltage level (referenced to V−) to the Enable pin.
Conversely, a TTL LOW voltage level (referenced to V−)
will disable the amplifier, reducing its supply current from
4.9mA to only 3.4µA per amplifier. Independent Enable
pins are available for each channel (dual version),
providing maximum design flexibility. For portable
battery-operated applications, this feature can be used to
greatly reduce the average current and thereby extend
battery life.
The Enable input can be modeled as a CMOS input gate
with a 100kΩ pull-up resistor to V+. This pin should be
connected to a valid high or low voltage or driven, not left
open circuit.
The enable time is 100ns and the disable time is only 30ns.
This allows the OPA357 to be operated as a gated
amplifier, or to have its output multiplexed onto a common
output bus. When disabled, the output assumes a
high-impedance state.
RAIL-TO-RAIL INPUT
The specified input common-mode voltage range of the
OPA357 extends 100mV beyond the supply rails. This is
achieved with a complementary input stagean
N-channel input differential pair in parallel with a
P-channel differential pair, as shown in Figure 1. The
N-channel pair is active for input voltages close to the
positive rail, typically (V+) − 1.2V to 100mV above the
positive supply, while the P-channel pair is on for inputs
from 100mV below the negative supply to approximately
(V+) − 1.2V. There is a small transition region, typically
(V+) − 1.5V to (V+) − 0.9V, in which both pairs are on. This
600mV transition region can vary ±500mV with process
variation. Thus, the transition region (both input stages on)
can range from (V+) − 2.0V to (V+) − 1.5V on the low end,
up to (V+) − 0.9V to (V+) − 0.4V on the high end.
A double-folded cascode adds the signal from the two
input pairs and presents a differential signal to the class AB
output stage.
V+
Reference
Current
VIN+
VIN−
VBIAS1
Class AB
Control
Circuitry
VO
VBIAS2
V−
(Ground)
Figure 1. Simplified Schematic
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RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors
is used to achieve rail-to-rail output. For high-impedance
loads (> 200Ω), the output voltage swing is typically
100mV from the supply rails. With 10Ω loads, a useful
output swing can be achieved while maintaining high
open-loop gain. See the typical characteristic curve Output
Voltage Swing vs Output Current.
R2
10kΩ
C1
200pF
+5V
1µF
R1
100kΩ
R 5 = 1Ω
OUTPUT DRIVE
OPA2357
The OPA357’s output stage can supply a continuous
output current of ±100mA and still provide approximately
2.7V of output swing on a 5V supply, as shown in Figure 2.
For maximum reliability, it is not recommended to run a
continuous DC current in excess of ±100mA. Refer to the
typical characteristic curve Output Voltage Swing vs
Output Current. For supplying continuous output currents
greater than ±100mA, the OPA357 may be operated in
parallel as shown in Figure 3.
R3
100kΩ
+
−
2V In = 200mA
Out, as Shown
R 6 = 1Ω
RSHUNT
1Ω
OPA2357
R4
10kΩ
The OPA357 will provide peak currents up to 200mA,
which corresponds to the typical short-circuit current.
Therefore, an on-chip thermal shutdown circuit is provided
to protect the OPA357 from dangerously high junction
temperatures. At 160°C, the protection circuit will shut
down the amplifier. Normal operation will resume when the
junction temperature cools to below 140°C.
Laser Diode
Figure 3. Parallel Operation
VIDEO
R2
1kΩ
+
−
C1
50pF
V1
5V
The OPA357 output stage is capable of driving standard
back-terminated 75Ω video cables, as shown in Figure 4.
By back-terminating a transmission line, it does not exhibit
a capacitive load to its driver. A properly back-terminated
75Ω cable does not appear as capacitance; it presents
only a 150Ω resistive load to the OPA357 output.
1µF
R1
10kΩ
V+
+5V
OPA357
+
VIN
R3
10kΩ
Video
In
V−
R4
1kΩ
−
1V In = 100mA
Out, as Shown
75Ω
75Ω
RSHUNT
OPA357
+2.5V
To enable,
connect to V+
or drive with logic.
604Ω
604Ω
Laser Diode
Video
Output
+2.5V
Figure 2. Laser Diode Driver
12
Figure 4. Single-Supply Video Line Driver
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The OPA357 can be used as an amplifier for RGB graphic
signals, which have a voltage of zero at the video black
level, by offsetting and AC-coupling the signal. See
Figure 5.
604Ω
+3V
+
V+
10nF
604Ω
75Ω
1/2
OPA2357
R1
Red(1)
1µF
Red
75Ω
R2
V+
R1
Green(1)
R2
604Ω
75Ω
1/2
OPA2357
Green
75Ω
604Ω
NOTE: (1) Source video signal offset
300mV above ground to accomodate
op amp swing−to−ground capability.
604Ω
+3V
+
V+
1µF
10nF
604Ω
75Ω
Blue(1)
R1
OPA357
Blue
75Ω
R2
Figure 5. RGB Cable Driver
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WIDEBAND VIDEO MULTIPLEXING
inputs to source onto a single line. This simple Wired-OR
Video Multiplexer can be easily implemented using the
OPA357; see Figure 6.
One common application for video speed amplifiers which
include an enable pin is to wire multiple amplifier outputs
together, then select which one of several possible video
+2.5V
+
49.9Ω
Signal #1
1µF
10nF
1µF
10nF
A
O PA357
+
−2.5V
1kΩ
49.9Ω
VOUT
1kΩ
49.9Ω
+2.5V
+
49.9Ω
Signal #2
1µF
10nF
1µF
10nF
B
O PA357
+
−2.5V
1kΩ
1kΩ
HCO4
BON
Select
AON
Figure 6. Multiplexed Output
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DRIVING ANALOG−TO−DIGITAL
CONVERTERS
The OPA357 series op amps offer 60ns of settling time to
0.01%, making them a good choice for driving high- and
medium-speed sampling A/D converters and reference
circuits. The OPA357 series provide an effective means of
buffering the A/D converter’s input capacitance and
resulting charge injection while providing signal gain.
See Figure 7 for the OPA357 driving an A/D converter.
With the OPA357 in an inverting configuration, a capacitor
across the feedback resistor can be used to filter
high-frequency noise in the signal; see Figure 7.
CAPACITIVE LOAD AND STABILITY
The OPA357 series op amps can drive a wide range of
capacitive loads. However, all op amps under certain
conditions may become unstable. Op amp configuration,
gain, and load value are just a few of the factors to consider
when determining stability. An op amp in unity-gain
configuration is most susceptible to the effects of
capacitive loading. The capacitive load reacts with the op
amp’s output resistance, along with any additional load
resistance, to create a pole in the small-signal response
that degrades the phase margin. Refer to the typical
characteristic curve Frequency Response for Various CL
for details.
The OPA357’s topology enhances its ability to drive
capacitive loads. In unity gain, these op amps perform well
with large capacitive loads. Refer to the typical
characteristic curves Recommended RS vs Capacitive
Load and Frequency Response vs Capacitive Load for
details.
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 10Ω to 20Ω resistor
in series with the output, as shown in Figure 8. This
significantly reduces ringing with large capacitive
loadssee the typical characteristic curve Frequency
Response vs Capacitive Load. However, if there is a
resistive load in parallel with the capacitive load, RS
creates a voltage divider. This introduces a DC error at the
output and slightly reduces output swing. This error may
be insignificant. For instance, with RL = 10kΩ and RS =
20Ω, there is only about a 0.2% error at the output.
+5V
330pF
5kΩ
5kΩ
VIN
VREF
V+
5kΩ
ADS7818, ADS7861,
or ADS7864
12−Bit A/D Converter
+In
OPA357
+2.5V
0.1µF
−In
GND
VIN = 0V to −5V for 0V to 5V output.
NOTE: A/D Converter Input = 0V to VREF
Figure 7. The OPA357 in Inverting Configuration Driving an A/D Converter
V+
RS
VOUT
OPA357
VIN
RL
CL
To enable,
connect to V+
or drive with logic.
Figure 8. Series Resistor in Unity-Gain Configuration Improves Capacitive Load Drive
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WIDEBAND TRANSIMPEDANCE AMPLIFIER
PCB LAYOUT
Wide bandwidth, low input bias current, and low input
voltage and current noise make the OPA357 an ideal
wideband photodiode transimpedance amplifier for
low-voltage single-supply applications. Low-voltage noise
is important because photodiode capacitance causes the
effective noise gain of the circuit to increase at high
frequency.
Good high-frequency printed circuit board (PCB) layout
techniques should be employed for the OPA357.
Generous use of ground planes, short and direct signal
traces, and a suitable bypass capacitor located at the V+
pin will assure clean, stable operation. Large areas of
copper also provides a means of dissipating heat that is
generated in normal operation.
The key elements to a transimpedance design, as shown
in Figure 9, are the expected diode capacitance (including
the parasitic input common-mode and differential-mode
input capacitance (2 + 2)pF for the OPA357), the desired
transimpedance gain (RF), and the Gain Bandwidth
Product (GBP) for the OPA357 (100MHz). With these 3
variables set, the feedback capacitor value (CF) may be set
to control the frequency response.
Sockets are definitely not recommended for use with any
high-speed amplifier.
CF
<1pF
(prevents gain peaking)
POWER DISSIPATION
RF
10MΩ
+V
λ
CD
OPA357
VOUT
To enable,
connect to V+
or drive with logic.
Figure 9. Transimpedance Amplifier
To achieve a maximally flat 2nd-order Butterworth
frequency response, the feedback pole should be set to:
1
+
2pR FCF
GBP
Ǹ4pR
C
F
D
(1)
Typical surface-mount resistors have a parasitic
capacitance of around 0.2pF that must be deducted from
the calculated feedback capacitance value.
Bandwidth is calculated by:
f *3dB +
GBP Hz
Ǹ2pR
C
F
D
(2)
For even higher transimpedance bandwidth, the
high-speed CMOS OPA355 (200MHz GBW) or the
OPA655 (400MHz GBW) may be used.
16
A 10nF ceramic bypass capacitor is the minimum
recommended value; adding a 1µF or larger tantalum
capacitor in parallel can be beneficial when driving a
low-resistance load. Providing adequate bypass
capacitance is essential to achieving very low harmonic
and intermodulation distortion.
Besides the regular SOT23-6 and MSOP-10, the single
and dual versions of the OPA357 also come in an SO-8
PowerPAD. The SO-8 PowerPAD is a standard-size SO-8
package where the exposed leadframe on the bottom of
the package is soldered directly to the PCB to create an
extremely low thermal resistance. This will enhance the
OPA357’s power dissipation capability significantly and
eliminates the use of bulky heatsinks and slugs
traditionally used in thermal packages. This package can
be easily mounted using standard PCB assembly
techniques. NOTE: Since the SO-8 PowerPAD is
pin-compatible with standard SO-8 packages, the
OPA357 can directly replace operational amplifiers in
existing sockets. Soldering the PowerPAD to the PCB is
always recommended, even with applications that have
low power dissipation. This provides the necessary
thermal and mechanical connection between the
leadframe die pad and the PCB.
For resistive loads, the maximum power dissipation occurs
at a DC output voltage of one-half the power-supply
voltage. Dissipation with AC signals is lower. Application
Bulletin AB-039 (SBOA022), Power Amplifier Stress and
Power Handling Limitations, explains how to calculate or
measure power dissipation with unusual signals and
loads, and can be found at www.ti.com.
Any tendency to activate the thermal protection circuit
indicates excessive power dissipation or an inadequate
heat sink. For reliable operation, junction temperature
should be limited to 150°C, maximum. To estimate the
margin of safety in a complete design, increase the
ambient temperature until the thermal protection is
triggered at 160°C. The thermal protection should trigger
more than 35°C above the maximum expected ambient
condition of your application.
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PowerPAD THERMALLY ENHANCED
PACKAGE
The OPA357 uses the SO-8 PowerPAD package, a
thermally enhanced, standard size IC package designed
to eliminate the use of bulky heatsinks and slugs
traditionally used in thermal packages. This package can
be easily mounted using standard PCB assembly
techniques.
The PowerPAD package is designed so that the leadframe
die pad (or thermal pad) is exposed on the bottom of the
IC, as shown in Figure 10. This provides an extremely low
thermal resistance (qJC) path between the die and the
exterior of the package. The thermal pad on the bottom of
the IC is then soldered directly to the PCB, using the PCB
as a heatsink. In addition, plated-through holes (vias)
provide a low thermal resistance heat flow path to the back
side of the PCB.
PowerPAD ASSEMBLY PROCESS
1. The PowerPAD must be connected to the device’s most
negative supply voltage, which will be ground in
single-supply applications, and V− in split−supply
applications.
2. Prepare the PCB with a top-side etch pattern, as shown
in Figure 11. The exact land design may vary based on the
specific assembly process requirements. There should be
etch for the leads as well as etch for the thermal land.
Thermal Land
(Copper)
Minimum Size
4.8mm x 3.8mm
(189 mils x 150 mils)
OPTIONAL:
Additional 4 vias outside
of thermal pad area but
under the package.
REQUIRED:
Thermal pad area 2.286mm x 2.286mm
(90 mils x 90 mils) with 5 vias
(via diameter = 13 mils)
Leadframe (Copper Alloy)
IC (Silicon)
Mold Compound (Plastic)
Die Attach (Epoxy)
Leadframe Die Pad
Exposed at Base of the Package
(Copper Alloy)
Figure 10. Section View of a PowerPAD Package
Figure 11. 8-Pin PowerPAD PCB Etch and Via
Pattern
3. Place the recommended number of plated-through
holes (or thermal vias) in the area of the thermal pad.
These holes should be 13 mils in diameter. They are kept
small so that solder wicking through the holes is not a
problem during reflow. The minimum recommended
number of holes for the SO-8 PowerPAD package is 5, as
shown in Figure 11.
4. It is recommended, but not required, to place a small
number of additional holes under the package and outside
the thermal pad area. These holes provide additional heat
paths between the copper thermal land and the ground
plane. They may be larger because they are not in the area
to be soldered, so wicking is not a problem. This is
illustrated in Figure 11.
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5. Connect all holes, including those within the thermal pad
area and outside the pad area, to the internal ground plane
or other internal copper plane for single-supply
applications, and to V− for split-supply applications.
6. When laying out these holes, do not use the typical web
or spoke via connection methodology, as shown in
Figure 12. Web connections have a high thermal
resistance connection that is useful for slowing the heat
transfer during soldering operations. This makes soldering
the vias that have ground plane connections easier.
However, in this application, low thermal resistance is
desired for the most efficient heat transfer. Therefore, the
holes under the PowerPAD package should make their
connection to the internal ground plane with a complete
connection around the entire circumference of the
plated-through hole.
Solid Via
RECOMMENDED
Web or Spoke Via
NOT RECOMMENDED
(due to poor heat conduction)
Figure 12. Internal ESD Protection
18
7. The top-side solder mask should leave the pad
connections and the thermal pad area exposed. The
thermal pad area should leave the 13 mil holes exposed.
The larger holes outside the thermal pad area may be
covered with solder mask.
8. Apply solder paste to the exposed thermal pad area and
all of the package terminals.
9. With these preparatory steps in place, the PowerPAD IC
is simply placed in position and run through the solder
reflow operation as any standard surface-mount
component. This results in a part that is properly installed.
For detailed information on the PowerPAD package
including thermal modeling considerations and repair
procedures, please see Technical Brief SLMA002,
PowerPAD Thermally Enhanced Package, located at
www.ti.com.
PACKAGE OPTION ADDENDUM
www.ti.com
10-May-2004
PACKAGING INFORMATION
ORDERABLE DEVICE
STATUS(1)
PACKAGE TYPE
PACKAGE DRAWING
PINS
PACKAGE QTY
OPA2357AIDGSR
ACTIVE
VSSOP
DGS
10
2500
OPA2357AIDGST
ACTIVE
VSSOP
DGS
10
250
OPA357AIDBVR
ACTIVE
SOP
DBV
6
3000
OPA357AIDBVT
ACTIVE
SOP
DBV
6
250
OPA357AIDDA
ACTIVE
HSOP
DDA
8
100
OPA357AIDDAR
ACTIVE
HSOP
DDA
8
2500
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
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