ETC OPA353NA/250

®
OPA353
OPA2353
OPA4353
OPA
235
3
OPA
435
3
OPA
43
53
For most current data sheet and other product
information, visit www.burr-brown.com
High-Speed, Single-Supply, Rail-to-Rail
OPERATIONAL AMPLIFIERS
MicroAmplifier ™ Series
FEATURES
APPLICATIONS
●
●
●
●
●
●
●
●
●
● CELL PHONE PA CONTROL LOOPS
● DRIVING A/D CONVERTERS
● VIDEO PROCESSING
● DATA ACQUISITION
● PROCESS CONTROL
● AUDIO PROCESSING
● COMMUNICATIONS
● ACTIVE FILTERS
● TEST EQUIPMENT
RAIL-TO-RAIL INPUT
RAIL-TO-RAIL OUTPUT (within 10mV)
WIDE BANDWIDTH: 44MHz
HIGH SLEW RATE: 22V/µs
LOW NOISE: 5nV/√Hz
LOW THD+NOISE: 0.0006%
UNITY-GAIN STABLE
MicroSIZE PACKAGES
SINGLE, DUAL, AND QUAD
DESCRIPTION
extends 300mV beyond the supply rails. Output voltage
swing is to within 10mV of the supply rails with a 10kΩ
load. Dual and quad designs feature completely independent circuitry for lowest crosstalk and freedom from
interaction.
The single (OPA353) packages are the tiny 5-lead SOT23-5 surface mount and SO-8 surface mount. The dual
(OPA2353) comes in the miniature MSOP-8 surface
mount and SO-8 surface mount. The quad (OPA4353)
packages are the space-saving SSOP-16 surface mount
and SO-14 surface mount. All are specified from –40°C
to +85°C and operate from –55°C to +125°C.
OPA353 series rail-to-rail CMOS operational amplifiers are designed for low cost, miniature applications.
They are optimized for low voltage, single-supply operation. Rail-to-rail input/output, low noise (5nV/√Hz),
and high speed operation (44MHz, 22V/µs) make them
ideal for driving sampling analog-to-digital converters.
They are also well suited for cell phone PA control
loops and video processing (75Ω drive capability) as
well as audio and general purpose applications. Single,
dual, and quad versions have identical specifications
for design flexibility.
The OPA353 series operates on a single supply as low as
2.5V with an input common-mode voltage range that
OPA4353
SPICE Model available at www.burr-brown.com
OPA353
NC
OPA353
Out 1
5
1
4
NC
2
7
V+
+In
3
6
Output
V–
4
5
NC
V+
–In
SO-8
1
16
Out D
–In A
2
15
–In D
+In A
3
14
+In D
+V
4
13
–V
+In B
5
12
+In C
A
–In
V– 2
+In 3
8
Out A
D
OPA2353
Out A
1
–In A
2
+In A
3
V–
4
A
B
8
V+
7
Out B
6
–In B
5
+In B
B
C
–In B
6
11
–In C
Out B
7
10
Out C
NC
8
9
NC
SSOP-16
SOT-23-5
SO-8, MSOP-8
(SO-14 package not shown)
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/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
© 1998 Burr-Brown Corporation
SBOS103
PDS-1479B
Printed in U.S.A. March, 1999
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 1kΩ connected to VS /2 and VOUT = VS /2, unless otherwise noted.
Boldface limits apply over the specified temperature range, TA = –40°C to +85°C. VS = 5V.
OPA353NA, UA
OPA2353EA, UA
OPA4353EA, UA
PARAMETER
CONDITION
OFFSET VOLTAGE
Input Offset Voltage
TA = –40°C to +85°C
vs Temperature
vs Power Supply Rejection Ratio
TA = –40°C to +85°C
Channel Separation (dual, quad)
VOS
PSRR
INPUT BIAS CURRENT
Input Bias Current
TA = –40°C to +85°C
Input Offset Current
±3
TA = –40°C to +85°C
VS = 2.7V to 5.5V, VCM = 0V
VS = 2.7V to 5.5V, VCM = 0V
dc
±5
40
±0.5
See Typical Curve
±0.5
I OS
in
VCM
CMRR
–0.1V < VCM < (V+) – 2.4V
VS = 5V, –0.1V < VCM < 5.1V
VS = 5V, –0.1V < VCM < 5.1V
RL = 10kΩ, 50mV < VO < (V+) – 50mV
RL = 10kΩ, 50mV < VO < (V+) – 50mV
RL = 1kΩ, 200mV < VO < (V+) – 200mV
RL = 1kΩ, 200mV < VO < (V+) – 200mV
AOL
TA = –40°C to +85°C
OUTPUT
Voltage Output Swing from Rail(4)
TA = –40°C to +85°C
TA = –40°C to +85°C
Output Current
Short-Circuit Current
Capacitive Load Drive
POWER SUPPLY
Operating Voltage Range
Minimum Operating Voltage
Quiescent Current (per amplifier)
TA = –40°C to +85°C
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance
SOT-23-5
MSOP-8 Surface Mount
SO-8 Surface Mount
SSOP-16 Surface Mount
SO-14 Surface Mount
GBW
SR
THD+N
UNITS
±8
mV
mV
µV/°C
µV/V
µV/V
µV/V
±10
150
175
±10
pA
±10
pA
µVrms
nV/√Hz
nV/√Hz
fA/√Hz
4
7
5
4
en
TA = –40°C to +85°C
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
Settling Time, 0.1%
0.01%
Overload Recovery Time
Total Harmonic Distortion + Noise
Differential Gain Error
Differential Phase Error
MAX
0.15
–0.1
76
60
58
INPUT IMPEDANCE
Differential
Common-Mode
OPEN-LOOP GAIN
Open-Loop Voltage Gain
TA = –40°C to +85°C
TYP(1)
VS = 5V
IB
NOISE
Input Voltage Noise, f = 100Hz to 400kHz
Input Voltage Noise Density, f = 10kHz
f = 100kHz
Current Noise Density, f = 10kHz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
MIN
100
100
100
100
CL = 100pF
G=1
G=1
G = ±1, 2V Step
G = ±1, 2V Step
VIN • G = VS
RL = 600Ω, VO = 2.5Vp-p(2), G = 1, f = 1kHz
G = 2, RL = 600Ω, VO = 1.4V (3)
G = 2, RL = 600Ω, VO = 1.4V (3)
VOUT
RL = 10kΩ, AOL ≥ 100dB
RL = 10kΩ, AOL ≥ 100dB
RL = 1kΩ, AOL ≥ 100dB
RL = 1kΩ, AOL ≥ 100dB
IQ
V
dB
dB
dB
1013 || 2.5
1013 || 6.5
Ω || pF
Ω || pF
122
dB
dB
dB
dB
120
10
25
MHz
V/µs
µs
µs
µs
%
%
deg
50
50
200
200
mV
mV
mV
mV
mA
mA
5.5
8
9
V
V
mA
mA
+85
+125
+125
°C
°C
°C
±40(5)
±80
See Typical Curve
CLOAD
TA = –40°C to +85°C
(V+) + 0.1
44
22
0.22
0.5
0.1
0.0006
0.17
0.17
I OUT
I SC
VS
86
74
2.7
2.5
5.2
IO = 0
IO = 0
–40
–55
–55
θJA
200
150
150
100
100
°C/W
°C/W
°C/W
°C/W
°C/W
NOTES: (1) VS = +5V. (2) VOUT = 0.25V to 2.75V. (3) NTSC signal generator used. See Figure 6 for test circuit. (4) Output voltage swings are measured between
the output and power supply rails. (5) See typical performance curve, “Output Voltage Swing vs Output Swing.”
®
OPA353, 2353, 4353
2
ELECTROSTATIC
DISCHARGE SENSITIVITY
PIN CONFIGURATION
Top View
SO-14
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.
OPA4353
Out A
1
–In A
2
A
14
Out D
13
–In D
D
+In A
3
12
+In D
V+
4
11
V–
+In B
5
10
+In C
B
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.
C
–In B
6
9
–In C
Out B
7
8
Out C
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage ................................................................................... 5.5V
Signal Input Terminals, Voltage(2) .................. (V–) – 0.3V to (V+) + 0.3V
Current(2) .................................................... 10mA
Output Short-Circuit(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.
Exposure to absolute maximum conditions for extended periods may degrade device reliability. (2) Input terminals are diode-clamped to the power
supply rails. Input signals that can swing more than 0.3V beyond the supply
rails should be current-limited to 10mA or less. (3) Short circuit to ground,
one amplifier per package.
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE
DRAWING
NUMBER(1)
Single
OPA353NA
5-Lead SOT-23-5
331
–40°C to +85°C
D53
"
"
"
"
"
OPA353UA
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER(2)
TRANSPORT
MEDIA
OPA353NA /250
OPA353NA /3K
OPA353UA
OPA353UA /2K5
Tape and Reel
Tape and Reel
Rails
Tape and Reel
OPA2353EA /250
OPA2353EA/2K5
OPA2353UA
OPA2353UA/2K5
Tape and Reel
Tape and Reel
Rails
Tape and Reel
OPA4353EA /250
OPA4353EA/2K5
OPA4353UA
OPA4353UA/2K5
Tape and Reel
Tape and Reel
Rails
Tape and Reel
SO-8 Surface Mount
182
–40°C to +85°C
OPA353UA
"
"
"
"
"
Dual
OPA2353EA
MSOP-8 Surface Mount
337
–40°C to +85°C
E53
"
"
"
"
"
OPA2353UA
SO-8 Surface Mount
182
–40°C to +85°C
OPA2353UA
"
"
"
"
"
Quad
OPA4353EA
SSOP-16 Surface Mount
322
–40°C to +85°C
OPA4353EA
"
"
"
"
"
OPA4353UA
SO-14 Surface Mount
235
–40°C to +85°C
OPA4353UA
"
"
"
"
"
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are
available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “OPA2353EA/2K5” will get a single
2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book.
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.
®
3
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS = +5V, and RL = 1kΩ connected to VS/2, unless otherwise noted.
POWER SUPPLY AND COMMON-MODE
REJECTION RATIO vs FREQUENCY
OPEN-LOOP GAIN/PHASE vs FREQUENCY
160
0
100
90
140
φ
–90
60
G
40
–135
PSRR, CMRR (dB)
100
80
PSRR
80
–45
Phase (°)
Voltage Gain (dB)
120
70
60
CMRR
(VS = +5V
VCM = –0.1V to 5.1V)
50
40
30
20
20
10
0
–180
0.1
1
10
100
1k
10k
100k
1M
10M
0
100M
10
100
1k
Frequency (Hz)
10k
100k
1M
10M
Frequency (Hz)
INPUT VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
CHANNEL SEPARATION vs FREQUENCY
10k
100k
140
130
100
1k
Voltage Noise
100
10
1
10
Channel Separation (dB)
1k
Current Noise
Current Noise (fA√Hz)
Voltage Noise (nV√Hz)
10k
120
110
100
90
80
Dual and Quad
Versions
70
1
10
100
1k
10k
100k
1M
0.1
10M
60
10
100
1k
Frequency (Hz)
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
0.01
G = 10, 3Vp-p (VO = 1V to 4V)
Harmonic Distortion (%)
THD+N (%)
RL = 600Ω
G = 100, 3Vp-p (VO = 1V to 4V)
G = 1, 3Vp-p (VO = 1V to 4V)
Input goes through transition region
0.001
0.1
(–60dBc)
0.001
(–100dBc)
1k
10k
100k
G=1
VO = 2.5Vp-p
RL = 600Ω
3rd Harmonic
10k
100k
Frequency (Hz)
Frequency (Hz)
®
OPA353, 2353, 4353
10M
2nd Harmonic
0.0001
(–120dBc) 1k
0.0001
100
1M
0.01
(–80dBc)
G = 1, 2.5Vp-p (VO = 0.25V to 2.75V)
Input does NOT go through transition region
10
100k
HARMONIC DISTORTION + NOISE vs FREQUENCY
1
(–40dBc)
1
0.1
10k
Frequency (Hz)
4
1M
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, VS = +5V, and RL = 1kΩ connected to VS/2, unless otherwise noted.
OPEN-LOOP GAIN vs TEMPERATURE
DIFFERENTIAL GAIN/PHASE vs RESISTIVE LOAD
130
0.5
Open-Loop Gain (dB)
0.4
Differential Gain (%)
Differential Phase (°)
G=2
VO = 1.4V
NTSC Signal Generator
See Figure 6 for test circuit.
Phase
0.3
0.2
Gain
125
RL = 1kΩ
RL = 10kΩ
120
RL = 600Ω
115
0.1
110
0
0
100 200 300 400
500 600
–75
700 800 900 1000
–50
–25
0
25
50
75
100
125
Temperature (°C)
Resistive Load (Ω)
COMMON-MODE AND POWER SUPPLY
REJECTION RATIO vs TEMPERATURE
SLEW RATE vs TEMPERATURE
90
110
40
35
CMRR, VS = 5V
(VCM = –0.1V to +5.1V)
100
90
PSRR
60
Slew Rate (V/µs)
70
30
PSRR (dB)
CMRR (dB)
80
80
Negative Slew Rate
25
Positive Slew Rate
20
15
10
5
50
–75
70
–50
–25
0
25
50
75
100
0
125
–75
–50
–25
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs TEMPERATURE
100
6.0
90
5.5
+ISC
IQ
60
Quiescent Current (mA)
70
Short-Circuit Current (mA)
Quiescent Current (mA)
80
–ISC
5.5
40
3.5
30
3.0
0
25
50
125
4.0
4.0
–25
100
4.5
50
–50
75
5.0
4.5
3.5
–75
50
Per Amplifier
6.5
5.0
25
QUIESCENT CURRENT vs SUPPLY VOLTAGE
7.0
6.0
0
Temperature (°C)
Temperature (°C)
75
100
125
2.0
Temperature (°C)
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Supply Voltage (V)
®
5
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, VS = +5V, and RL = 1kΩ connected to VS/2, unless otherwise noted.
INPUT BIAS CURRENT
vs INPUT COMMON-MODE VOLTAGE
1k
1.5
100
1.0
Input Bias Current (pA)
Input Bias Current (pA)
INPUT BIAS CURRENT vs TEMPERATURE
10
1
0.5
0.0
0.1
–75
–50
–25
0
25
50
Temperature (°C)
75
100
–0.5
–0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
125
Common-Mode Voltage (V)
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
6
10
5
Output Voltage (Vp-p)
Output Impedance (Ω)
CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY
100
1
0.1
G = 100
0.01
G = 10
0.001
G=1
10
Maximum output
voltage without
slew rate-induced
distortion.
4
VS = 2.7V
3
2
1
0
100k
0.0001
1
VS = 5.5V
100
1k
10k
100k
1M
10M
100M
1M
Frequency (Hz)
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
100M
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
140
V+
(V+)–1
Open-Loop Gain (dB)
(V+)–2
+25°C
–55°C
+125°C
Depending on circuit configuration
(including closed-loop gain) performance
may be degraded in shaded region.
(V–)+2
+25°C
+125°C
–55°C
IOUT = 2.5mA
IOUT = 250µA
130
Output Voltage (V)
10M
Frequency (Hz)
120
110
IOUT = 4.2mA
100
90
80
(V–)+1
70
60
(V–)
±10
0
±20
±30
±40
0
Output Current (mA)
40
60
80
100 120
140 160 180 200
Output Voltage Swing from Supply Rails (mV)
®
OPA353, 2353, 4353
20
6
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, VS = +5V, and RL = 1kΩ connected to VS/2, unless otherwise noted.
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
35
25
Typical production
distribution of
packaged units.
Percent of Amplifiers (%)
Percent of Units (%)
20
Typical production
distribution of
packaged units.
30
15
10
5
25
20
15
10
5
0
0
–8 –7 –6 –5 4 –3 –2 –1 0
1
2
3
4
5
6
0
7 8
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Offset Voltage Drift (µV/°C)
Offset Voltage (mV)
SETTLING TIME vs CLOSED-LOOP GAIN
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
10
80
70
G=1
Settling Time (µs)
50
G = –1
40
30
G = ±10
20
0.01%
1
10
0.1%
0.1
0
10
100
1k
10k
100k
±1
1M
±10
Load Capacitance (pF)
Closed-Loop Gain (V/V)
SMALL-SIGNAL STEP RESPONSE
CL = 100pF
LARGE-SIGNAL STEP RESPONSE
CL = 100pF
±100
1V/div
50mV/div
Overshoot (%)
60
200ns/div
100ns/div
®
7
OPA353, 2353, 4353
APPLICATIONS INFORMATION
the OPA353 in unity-gain configuration. Operation is
from a single +5V supply with a 1kΩ load connected to
VS /2. The input is a 5Vp-p sinusoid. Output voltage is
approximately 4.95Vp-p.
OPA353 series op amps are fabricated on a state-of-the-art
0.6 micron CMOS process. They are unity-gain stable and
suitable for a wide range of general purpose applications.
Rail-to-rail input/output make them ideal for driving sampling A/D converters. They are well suited for controlling
the output power in cell phones. These applications often
require high speed and low noise. In addition, the OPA353
series offers a low cost solution for general purpose and
consumer video applications (75Ω drive capability).
Power supply pins should be bypassed with 0.01µF ceramic
capacitors.
OPERATING VOLTAGE
OPA353 series op amps are fully specified from +2.7V to
+5.5V. However, supply voltage may range from +2.5V to
+5.5V. Parameters are guaranteed over the specified supply
range—a unique feature of the OPA353 series. In addition,
many specifications apply from –40°C to +85°C. Most
behavior remains virtually unchanged throughout the full
operating voltage range. Parameters which vary significantly with operating voltages or temperature are shown in
the typical performance curves.
Excellent ac performance makes the OPA353 series well
suited for audio applications. Their bandwidth, slew rate,
low noise (5nV/√Hz), low THD (0.0006%), and small package options are ideal for these applications. The class AB
output stage is capable of driving 600Ω loads connected to
any point between V+ and ground.
Rail-to-rail input and output swing significantly increases
dynamic range, especially in low voltage supply applications. Figure 1 shows the input and output waveforms for
RAIL-TO-RAIL INPUT
The guaranteed input common-mode voltage range of the
OPA353 series 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 (see Figure 2). The N-channel pair is active
for input voltages close to the positive rail, typically
(V+) – 1.8V to 100mV above the positive supply, while the
P-channel pair is on for inputs from 100mV below the
negative supply to approximately (V+) – 1.8V. There is a
small transition region, typically (V+) – 2V to (V+) – 1.6V, in
which both pairs are on. This 400mV transition region can
vary ±400mV with process variation. Thus, the transition
region (both input stages on) can range from (V+) – 2.4V to
(V+) – 2.0V on the low end, up to (V+) – 1.6V to (V+) – 1.2V
on the high end.
VS = +5, G = +1, RL = 1kΩ
5V
1.25V/div
VIN
0
5V
VOUT
0
FIGURE 1. Rail-to-Rail Input and Output.
V+
Reference
Current
VIN+
VIN–
VBIAS1
VBIAS2
V–
(Ground)
FIGURE 2. Simplified Schematic.
®
OPA353, 2353, 4353
8
Class AB
Control
Circuitry
VO
FEEDBACK CAPACITOR IMPROVES RESPONSE
A double-folded cascode adds the signal from the two input
pairs and presents a differential signal to the class AB output
stage. Normally, input bias current is approximately 500fA.
However, large inputs (greater than 300mV beyond the
supply rails) can turn on the OPA353’s input protection
diodes, causing excessive current to flow in or out of the
input pins. Momentary voltages greater than 300mV beyond
the power supply can be tolerated if the current on the input
pins is limited to 10mA. This is easily accomplished with an
input resistor as shown in Figure 3. Many input signals are
inherently current-limited to less than 10mA, therefore, a
limiting resistor is not required.
For optimum settling time and stability with high-impedance feedback networks, it may be necessary to add a
feedback capacitor across the feedback resistor, RF, as
shown in Figure 4. This capacitor compensates for the zero
created by the feedback network impedance and the
OPA353’s input capacitance (and any parasitic layout
capacitance). The effect becomes more significant with
higher impedance networks.
CF
RIN
RF
VIN
V+
IOVERLOAD
10mA max
OPAx353
V+
CIN
VOUT
RIN • CIN = RF • CF
VIN
5kΩ
VOUT
OPA353
CL
CIN
FIGURE 3. Input Current Protection for Voltages Exceeding
the Supply Voltage.
Where CIN is equal to the OPA353’s input
capacitance (approximately 9pF) plus any
parastic layout capacitance.
RAIL-TO-RAIL OUTPUT
FIGURE 4. Feedback Capacitor Improves Dynamic Performance.
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. For light resistive loads
(>10kΩ), the output voltage swing is typically ten millivolts
from the supply rails. With heavier resistive loads (600Ω to
10kΩ), the output can swing to within a few tens of millivolts from the supply rails and maintain high open-loop
gain. See the typical performance curves “Output Voltage
Swing vs Output Current” and “Open-Loop Gain vs Output
Voltage.”
It is suggested that a variable capacitor be used for the
feedback capacitor since input capacitance may vary between op amps and layout capacitance is difficult to
determine. For the circuit shown in Figure 4, the value of
the variable feedback capacitor should be chosen so that
the input resistance times the input capacitance of the
OPA353 (typically 9pF) plus the estimated parasitic layout
capacitance equals the feedback capacitor times the feedback resistor:
CAPACITIVE LOAD AND STABILITY
RIN • CIN = RF • CF
OPA353 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 the
most susceptible to the effects of capacitive load. The
capacitive load reacts with the op amp’s output impedance,
along with any additional load resistance, to create a pole in
the small-signal response which degrades the phase margin.
where CIN is equal to the OPA353’s input capacitance
(sum of differential and common-mode) plus the layout
capacitance. The capacitor can be varied until optimum
performance is obtained.
In unity gain, OPA353 series op amps perform well with
large capacitive loads. Increasing gain enhances the
amplifier’s ability to drive more capacitance. The typical
performance curve “Small-Signal Overshoot vs Capacitive
Load” shows performance with a 1kΩ resistive load. Increasing load resistance improves capacitive load drive capability.
OPA353 series op amps are optimized for driving medium
speed (up to 500kHz) sampling A/D converters. However,
they also offer excellent performance for higher speed
converters. The OPA353 series provides an effective means
of buffering the A/D’s input capacitance and resulting
charge injection while providing signal gain. For applications requiring high accuracy, the OPA350 series is recommended.
DRIVING A/D CONVERTERS
®
9
OPA353, 2353, 4353
from becoming too high, which can cause stability problems when driving capacitive loads. As mentioned previously, the OPA353 has excellent capacitive load drive
capability for an op amp with its bandwidth.
Figure 5 shows the OPA353 driving an ADS7861. The
ADS7861 is a dual, 12-bit, 500kHz sampling converter in
the small SSOP-24 package. When used with the miniature
package options of the OPA353 series, the combination is
ideal for space-limited and low power applications. For
further information consult the ADS7861 data sheet.
VIDEO LINE DRIVER
Figure 6 shows a circuit for a single supply, G = 2 composite video line driver. The synchronized outputs of a
composite video line driver extend below ground. As
shown, the input to the op amp should be ac-coupled and
shifted positively to provide adequate signal swing to
account for these negative signals in a single-supply configuration.
OUTPUT IMPEDANCE
The low frequency open-loop output impedance of the
OPA353’s common-source output stage is approximately
1kΩ. When the op amp is connected with feedback, this
value is reduced significantly by the loop gain of the op
amp. For example, with 122dB of open-loop gain, the
output impedance is reduced in unity-gain to less than
0.001Ω. For each decade rise in the closed-loop gain, the
loop gain is reduced by the same amount which results in
a ten-fold increase in output impedance (see the typical
performance curve, “Output Impedance vs Frequency”).
The input is terminated with a 75Ω resistor and ac-coupled
with a 47µF capacitor to a voltage divider that provides the
dc bias point to the input. In Figure 6, this point is
approximately (V–) + 1.7V. Setting the optimal bias point
requires some understanding of the nature of composite
video signals. For best performance, one should be careful
to avoid the distortion caused by the transition region of
the OPA353’s complementary input stage. Refer to the
discussion of rail-to-rail input.
At higher frequencies, the output impedance will rise as
the open-loop gain of the op amp drops. However, at these
frequencies the output also becomes capacitive due to
parasitic capacitance. This prevents the output impedance
CB1
+5V
2kΩ
2kΩ
2
4
1/4
3 OPA4353
VIN B1
0.1µF
0.1µF
CB0
24
2kΩ
2kΩ
2
3
6
7
1/4
5 OPA4353
VIN B0
4
5
6
CA1
7
2kΩ
2kΩ
8
9
9
10
8
1/4
10 OPA4353
VIN A1
11
Serial Data A
CH B1–
Serial Data B
CH B0+
BUSY
CH B0–
CLOCK
CH A1+
1/4
OPA4353
VIN A0
14
11
VIN = 0V to 2.45V for 0V to 4.9V output.
Choose CB1, CB0, CA1, CA0 to filter high frequency noise.
FIGURE 5. OPA4353 Driving Sampling A/D Converter.
®
OPA353, 2353, 4353
10
CS
ADS7861
CH A1–
RD
CH A0+
CONVST
CH A0–
A0
REFIN
M0
REFOUT
M1
1
2kΩ
+VA
CH B1+
DGND
CA0
2kΩ
13
+VD
AGND
12
23
22
21
20
19
18
17
16
15
14
Serial
Interface
RF
1kΩ
RG
1kΩ
C4
0.1µF
+5V
C1
220µF
+
0.1µF
10µF
7
C2
47µF
Video
In
C5
1000µF
6
OPA353
ROUT
Cable
VOUT
RL
R1
75Ω
R2
5kΩ
4
R3
5kΩ
+5V (pin 7)
R4
5kΩ
C3
10µF
FIGURE 6. Single-Supply Video Line Driver.
+5V
50kΩ
(2.5V)
8
RG
REF1004-2.5
R1
100kΩ
4
R2
25kΩ
+5V
R3
25kΩ
1/2
OPA2353
R4
100kΩ
1/2
OPA2353
G=5+
VOUT
RL
10kΩ
200kΩ
RG
FIGURE 7. Two Op-Amp Instrumentation Amplifier With Improved High Frequency Common-Mode Rejection.
<1pF (prevents gain peaking)
R1
10.5kΩ
10MΩ
+V
+2.5V
λ
VO
OPA353
C1
1830pF
C2
270pF
FIGURE 8. Transimpedance Amplifier.
R2
49.9kΩ
VOUT
OPA353
VIN
RL
20kΩ
–2.5V
C1
4.7µF
+2.5V
FIGURE 10. 10kHz High-Pass Filter.
R1
2.74kΩ
R2
19.6kΩ
VOUT
OPA353
RL
20kΩ
VIN
C2
1nF
–2.5V
FIGURE 9. 10kHz Low-Pass Filter.
®
11
OPA353, 2353, 4353
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