High-Speed, Single-Supply, Rail-to-Rail

OPERATIONAL AMPLIFIERS

Micro

Amplifier

Series

Out D

In D

+In D

+In C

In C

Out C

Out A

In A

+In A

+In B

In B

Out B

OPA4350

SSOP-16

Out D

In D

+In D

+In C

In C

Out C

Out A

In A

+In A

V+

+In B

In B

Out B

OPA4350

SO-14

APPLICATIONS

CELL PHONE PA CONTROL LOOPS

DRIVING A/D CONVERTERS

VIDEO PROCESSING

DATA ACQUISITION

PROCESS CONTROL

AUDIO PROCESSING

COMMUNICATIONS

ACTIVE FILTERS

TEST EQUIPMENT

DESCRIPTION

OPA350 series rail-to-rail CMOS operational amplifi-
ers are optimized for low voltage, single-supply opera-
tion. Rail-to-rail input/output, low noise (5nV/

Hz),

and high speed operation (38MHz, 22V/

s) make them

ideal for driving sampling analog-to-digital converters.
They are also well suited for cell phone PA control
loops and video processing (75

drive capability) as

well as audio and general purpose applications. Single,
dual, and quad versions have identical specifications
for maximum design flexibility.

The OPA350 series operates on a single supply as low as
2.5V with an input common-mode voltage range that

extends 300mV below ground and 300mV above the
positive supply. Output voltage swing is to within 10mV
of the supply rails with a 10k

load. Dual and quad

designs feature completely independent circuitry for low-
est crosstalk and freedom from interaction.

The single (OPA350) and dual (OPA2350) come in
the miniature MSOP-8 surface mount, SO-8 surface
mount, and 8-pin DIP packages. The quad (OPA4350)
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

PDS-1470B

Printed in U.S.A. March, 1999

OPA350

OPA2350
OPA4350

FEATURES

RAIL-TO-RAIL INPUT

RAIL-TO-RAIL OUTPUT (within 10mV)

WIDE BANDWIDTH: 38MHz

HIGH SLEW RATE: 22V/

LOW NOISE: 5nV/

LOW THD+NOISE: 0.0006%

UNITY-GAIN STABLE

Micro

SIZE PACKAGES

SINGLE, DUAL, AND QUAD

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

V+

Output

+In

OPA350

8-Pin DIP, SO-8, MSOP-8

V+

Out B

In B

+In B

Out A

In A

+In A

OPA2350

8-Pin DIP, SO-8, MSOP-8

OPA350

OPA2350

OPA4350

OPA

4350

For most current data sheet and other product

information, visit www.burr-brown.com

SPICE Model available at www.burr-brown.com

OPA350, 2350, 4350

OPA350EA, UA, PA

OPA2350EA, UA, PA

OPA4350EA, UA

SPECIFICATIONS: V

= 2.7V to 5.5V

At T

= +25

C, R

= 1k

connected to V

/ 2 and V

OUT

= V

/2, unless otherwise noted.

Boldface limits apply over the specified temperature range, T

= 40

C to +85

C. V

= 5V.

PARAMETER

CONDITION

MIN

TYP

(1)

MAX

UNITS

OFFSET VOLTAGE
Input Offset Voltage

= 5V

150

500

= 40

C to +85

vs Temperature

= 40

C to +85

vs Power Supply Rejection Ratio

PSRR

= 2.7V to 5.5V, V

= 0V

150

V/V

= 40

C to +85

= 2.7V to 5.5V, V

= 0V

175

V/V

Channel Separation (dual, quad)

0.15

V/V

INPUT BIAS CURRENT
Input Bias Current

0.5

vs Temperature

See Typical Performance Curve

Input Offset Current

0.5

NOISE
Input Voltage Noise, f = 100Hz to 400kHz

Vrms

Input Voltage Noise Density, f = 10kHz

nV/

f = 100kHz

nV/

Current Noise Density, f = 10kHz

fA/

INPUT VOLTAGE RANGE
Common-Mode Voltage Range

= 40

C to +85

0.1

(V+)+0.1

Common-Mode Rejection Ratio

CMRR

= 2.7V, 0.1V < V

< 2.8V

= 5.5V, 0.1V < V

< 5.6V

= 40

C to +85

= 5.5V, 0.1V < V

< 5.6V

INPUT IMPEDANCE
Differential

|| 2.5

|| pF

Common-Mode

|| 6.5

|| pF

OPEN-LOOP GAIN
Open-Loop Voltage Gain

= 10k

, 50mV < V

< (V+) 50mV

100

122

= 40

C to +85

= 10k

, 50mV < V

< (V+) 50mV

100

= 1k

, 200mV < V

< (V+) 200mV

100

120

= 40

C to +85

= 1k

, 200mV < V

< (V+) 200mV

100

FREQUENCY RESPONSE

= 100pF

Gain-Bandwidth Product

GBW

G = 1

MHz

Slew Rate

G = 1

Settling Time, 0.1%

G =

1, 2V Step

0.22

0.01%

G =

1, 2V Step

0.5

Overload Recovery Time

· G = V

0.1

Total Harmonic Distortion + Noise

THD+N

= 600

, V

= 2.5Vp-p

(2)

, G = 1, f = 1kHz

0.0006

Differential Gain Error

G = 2, R

= 600

, V

= 1.4V

(3)

0.17

Differential Phase Error

G = 2, R

= 600

, V

= 1.4V

(3)

0.17

deg

OUTPUT
Voltage Output Swing from Rail

(4)

OUT

= 10k

, A

100dB

= 40

C to +85

= 10k

100dB

= 1k

100dB

200

= 40

C to +85

= 1k

, A

100dB

200

Output Current

OUT

(5)

Short-Circuit Current

Capacitive Load Drive

LOAD

See Typical Curve

POWER SUPPLY
Operating Voltage Range

= 40

C to +85

2.7

5.5

Minimum Operating Voltage

2.5

Quiescent Current (per amplifier)

= 0

5.2

7.5

= 40

C to +85

= 0

8.5

TEMPERATURE RANGE
Specified Range

+85

Operating Range

+125

Storage Range

+125

Thermal Resistance

MSOP-8 Surface Mount

150

C/W

SO-8 Surface Mount

150

C/W

8-Pin DIP

100

C/W

SO-14 Surface Mount

100

C/W

SSOP-16 Surface Mount

100

C/W

NOTES: (1) V

= +5V. (2) V

OUT

= 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 Current."

OPA350, 2350, 4350

PACKAGE

SPECIFIED

DRAWING

TEMPERATURE

PACKAGE

ORDERING

TRANSPORT

PRODUCT

PACKAGE

NUMBER

(1)

RANGE

MARKING

NUMBER

(2)

MEDIA

Single
OPA350EA

MSOP-8 Surface Mount

337

C to +85

C50

OPA350EA/250

Tape and Reel

OPA350EA/2K5

Tape and Reel

OPA350UA

SO-8 Surface-Mount

182

C to +85

OPA350UA

Rails

OPA350UA/2K5

Tape and Reel

OPA350PA

8-Pin DIP

006

C to +85

OPA350PA

Rails

Dual
OPA2350EA

MSOP-8 Surface-Mount

337

C to +85

D50

OPA2350EA/250

Tape and Reel

OPA2350EA/2K5

Tape and Reel

OPA2350UA

SO-8 Surface-Mount

182

C to +85

OPA2350UA

Rails

OPA2350UA/2K5

Tape and Reel

OPA2350PA

8-Pin DIP

006

C to +85

OPA2350PA

Rails

Quad
OPA4350EA

SSOP-16 Surface-Mount

322

C to +85

OPA4350EA

OPA4350EA/250

Tape and Reel

OPA4350EA/2K5

Tape and Reel

OPA4350UA

SO-14 Surface Mount

235

C to +85

OPA4350UA

Rails

OPA4350UA/2K5

Tape and Reel

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 "OPA2350EA/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.

PACKAGE/ORDERING INFORMATION

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

Storage Temperature ..................................................... 55

C to +125

Junction Temperature ...................................................................... 150

Lead Temperature (soldering, 10s) ................................................. 300

NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may de-
grade 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.

ABSOLUTE MAXIMUM RATINGS

(1)

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.

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.

OPA350, 2350, 4350

TYPICAL PERFORMANCE CURVES

At T

= +25

C, V

= +5V, and R

= 1k

connected to V

/2, unless otherwise noted.

POWER SUPPLY AND COMMON-MODE

REJECTION RATIO vs FREQUENCY

100

PSRR, CMRR (dB)

Frequency (Hz)

100

10k

100k

10M

PSRR

CMRR

= +5V

= 0.1V to 5.1V)

INPUT VOLTAGE AND CURRENT NOISE

SPECTRAL DENSITY vs FREQUENCY

100k

10k

100

10k

100

0.1

Voltage Noise (nV

Hz)

Frequency (Hz)

100

10k

100k

10M

Current Noise (fA

Hz)

Voltage Noise

Current Noise

CHANNEL SEPARATION vs FREQUENCY

Frequency (Hz)

Channel Separation (dB)

140

130

120

110

100

100k

10k

10M

Dual and quad devices.

HARMONIC DISTORTION + NOISE vs FREQUENCY

(40dBc)

0.1

(60dBc)

0.01

(80dBc)

0.001

(100dBc)

0.0001

(120dBc)

Harmonic Distortion (%)

Frequency (Hz)

10k

100k

G = 1
V

= 2.5Vp-p

= 600

3rd Harmonic

2nd Harmonic

OPEN-LOOP GAIN/PHASE vs FREQUENCY

0.1

160

140

120

100

Voltage Gain (dB)

135

180

Phase (

)

Frequency (Hz)

100

10k

100k

10M

100M

TOTAL HARMONIC DISTORTION + NOISE

vs FREQUENCY

0.1

0.01

0.001

0.0001

THD+N (%)

Frequency (Hz)

100

10k

100k

= 600

G = 100, 3Vp-p (V

= 1V to 4V)

G = 10, 3Vp-p (V

= 1V to 4V)

G = 1, 3Vp-p (V

= 1V to 4V)

Input goes through transition region

G = 1, 2.5Vp-p (V

= 0.25V to 2.75V)

Input does NOT go through transition region

OPA350, 2350, 4350

TYPICAL PERFORMANCE CURVES

(CONT)

At T

= +25

C, V

= +5V, and R

= 1k

connected to V

/2, unless otherwise noted.

OPEN-LOOP GAIN vs TEMPERATURE

130

125

120

115

110

Open-Loop Gain (dB)

Temperature (

100

125

= 600

= 1k

= 10k

SLEW RATE vs TEMPERATURE

Temperature (

Slew Rate (V/

100

125

Negative Slew Rate

Positive Slew Rate

DIFFERENTIAL GAIN/PHASE vs RESISTIVE LOAD

0.5

0.4

0.3

0.2

0.1

Differential Gain (%)

Differential Phase (

)

Resistive Load (

)

100

200

300

500

400

600

800

700

900 1000

G = 2
V

= 1.4V

NTSC Signal Generator
See Figure 6 for test circuit.

Phase

Gain

COMMON-MODE AND POWER SUPPLY REJECTION RATIO

vs TEMPERATURE

100

CMRR (dB)

110

100

PSRR (dB)

Temperature (

100

125

CMRR, V

= 5.5V

= 0.1V to +5.6V)

CMRR, V

= 2.7V

= 0.1V to +2.8V)

PSRR

QUIESCENT CURRENT AND

SHORT-CIRCUIT CURRENT vs TEMPERATURE

Temperature (

Quiescent Current (mA)

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

100

Short-Circuit Current (mA)

100

125

QUIESCENT CURRENT vs SUPPLY VOLTAGE

Supply Voltage (V)

Quiescent Current (mA)

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

Per Amplifier

OPA350, 2350, 4350

TYPICAL PERFORMANCE CURVES

(CONT)

At T

= +25

C, V

= +5V, and R

= 1k

connected to V

/2, unless otherwise noted.

INPUT BIAS CURRENT vs TEMPERATURE

Input Bias Current (pA)

Temperature (

100

125

100

0.1

INPUT BIAS CURRENT

vs INPUT COMMON-MODE VOLTAGE

Common-Mode Voltage (V)

Input Bias Current (pA)

1.5

1.0

0.5

0.0

0.5

0.5 0.0 0.5 1.0

2.0

1.5

2.5 3.0 3.5 4.0

5.0

4.5

5.5

CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY

Frequency (Hz)

Output Impedance (

)

100

0.1

0.01

0.001

0.0001

100

10k

100k

10M

100M

G = 100

G = 10

G = 1

MAXIMUM OUTPUT VOLTAGE vs FREQUENCY

100M

10M

Frequency (Hz)

100k

Output Voltage (Vp-p)

Maximum output
voltage without
slew rate-induced
distortion.

= 2.7V

= 5.5V

OUTPUT VOLTAGE SWING vs OUTPUT CURRENT

Output Current (mA)

Output Voltage (V)

V+

(V+)1

(V+)2

(V)+2

(V)+1

(V)

+25

+125

+25

Depending on circuit configuration
(including closed-loop gain) performance
may be degraded in shaded region.

OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING

140

130

120

110

100

Open-Loop Gain (dB)

Output Voltage Swing from Rails (mV)

100

120

160

140

180

200

OUT

= 4.2mA

OUT

= 250

OUT

= 2.5mA

OPA350, 2350, 4350

TYPICAL PERFORMANCE CURVES

(CONT)

At T

= +25

C, V

= +5V, and R

= 1k

connected to V

/2, unless otherwise noted.

SMALL-SIGNAL STEP RESPONSE

= 100pF

100ns/div

50mV/div

SETTLING TIME vs CLOSED-LOOP GAIN

0.1

Settling Time (

Closed-Loop Gain (V/V)

100

0.1%

0.01%

LARGE-SIGNAL STEP RESPONSE

= 100pF

200ns/div

1V/div

SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE

100

10k

100k

Load Capacitance (pF)

Overshoot (%)

G = 1

G =

Offset Voltage (

OFFSET VOLTAGE

PRODUCTION DISTRIBUTION

Percent of Amplifiers (%)

500

450

400

350

300

250

200

150

100

150

200

250

300

350

400

450

500

Typical distribution of

packaged units.

Offset Voltage Drift (

OFFSET VOLTAGE DRIFT

PRODUCTION DISTRIBUTION

10 11 12 13 14 15

Percent of Amplifiers (%)

Typical production
distribution of
packaged units.

OPA350, 2350, 4350

APPLICATIONS INFORMATION

OPA350 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 sam-
pling A/D converters. They are also well suited for control-
ling the output power in cell phones. These applications
often require high speed and low noise. In addition, the
OPA350 series offers a low cost solution for general purpose
and consumer video applications (75

drive capability).

Excellent ac performance makes the OPA350 series well
suited for audio applications. Their bandwidth, slew rate,
low noise (5nV/

Hz), low THD (0.0006%), and small pack-

age options are ideal for these applications. The class AB
output stage is capable of driving 600

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 applica-
tions. Figure 1 shows the input and output waveforms for

FIGURE 2. Simplified Schematic.

= +5, G = +1, R

= 1k

1.25V/div

FIGURE 1. Rail-to-Rail Input and Output.

BIAS1

BIAS2

Class AB

Control

Circuitry

(Ground)

V+

Reference

Current

OUT

the OPA350 in unity-gain configuration. Operation is
from a single +5V supply with a 1k

load connected to

/2. The input is a 5Vp-p sinusoid. Output voltage swing

is approximately 4.95Vp-p.

Power supply pins should be bypassed with 0.01

F ceramic

capacitors.

OPERATING VOLTAGE

OPA350 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 OPA350 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 signifi-
cantly with operating voltage or temperature are shown in
the typical performance curves.

RAIL-TO-RAIL INPUT

The guaranteed input common-mode voltage range of the
OPA350 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.

OPA350, 2350, 4350

OPA350 series op amps are laser-trimmed to reduce offset
voltage difference between the N-channel and
P-channel input stages, resulting in improved common-
mode rejection and a smooth transition between the
N-channel pair and the P-channel pair. However, within the
400mV transition region PSRR, CMRR, offset voltage,
offset drift, and THD may be degraded compared to opera-
tion outside this region.

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 OPA350'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.

performance curve "Small-Signal Overshoot vs Capacitive
Load" shows performance with a 1k

resistive load. In-

creasing load resistance improves capacitive load drive ca-
pability.

FEEDBACK CAPACITOR IMPROVES RESPONSE

For optimum settling time and stability with high-imped-
ance feedback networks, it may be necessary to add a
feedback capacitor across the feedback resistor, R

, as

shown in Figure 4. This capacitor compensates for the zero
created by the feedback network impedance and the
OPA350's input capacitance (and any parasitic layout
capacitance). The effect becomes more significant with
higher impedance networks.

FIGURE 3. Input Current Protection for Voltages Exceeding

the Supply Voltage.

RAIL-TO-RAIL OUTPUT

A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. For light resistive loads
(>10k

), the output voltage swing is typically a ten milli-

volts from the supply rails. With heavier resistive loads
(600

to 10k

), 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."

CAPACITIVE LOAD AND STABILITY

OPA350 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 determin-
ing 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.

In unity gain, OPA350 series op amps perform well with
very large capacitive loads. Increasing gain enhances the
amplifier's ability to drive more capacitance. The typical

FIGURE 4. Feedback Capacitor Improves Dynamic Perfor-

mance.

OPAx350

10mA max

V+

OUT

OVERLOAD

It is suggested that a variable capacitor be used for the
feedback capacitor since input capacitance may vary be-
tween 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
OPA350 (typically 9pF) plus the estimated parasitic layout
capacitance equals the feedback capacitor times the feed-
back resistor:

· C

= R

· C

where C

is equal to the OPA350's input capacitance

(sum of differential and common-mode) plus the layout
capacitance. The capacitor can be varied until optimum
performance is obtained.

DRIVING A/D CONVERTERS

OPA350 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 OPA350 series provides an effective means
of buffering the A/D's input capacitance and resulting
charge injection while providing signal gain.

OPA350

V+

OUT

· C

= R

Where C

is equal to the OPA350's input

capacitance (approximately 9pF) plus any
parastic layout capacitance.

OPA350, 2350, 4350

FIGURE 5. OPA4350 Driving Sampling A/D Converter.

Figure 5 shows the OPA350 driving an ADS7861. The
ADS7861 is a dual, 500kHz 12-bit sampling converter in
the tiny SSOP-24 package. When used with the miniature
package options of the OPA350 series, the combination is
ideal for space-limited applications. For further informa-
tion, consult the ADS7861 data sheet.

OUTPUT IMPEDANCE

The low frequency open-loop output impedance of the
OPA350's common-source output stage is approximately
1k

. 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
0.001

. 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 effective output impedance (see the
typical performance curve, "Output Impedance vs Fre-
quency").

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

from becoming too high, which can cause stability prob-
lems when driving capacitive loads. As mentioned previ-
ously, the OPA350 has excellent capacitive load drive
capability for an op amp with its bandwidth.

VIDEO LINE DRIVER

Figure 6 shows a circuit for a single supply, G = 2 com-
posite 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 con-
figuration.

The input is terminated with a 75

resistor and ac-coupled

with a 47

F 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 OPA350's complementary input stage. Refer to the
discussion of rail-to-rail input.

1/4

OPA4350

CH B1+

CH B1

CH B0+

CH B0

CH A1+

CH A1

CH A0+

CH A0

REF

OUT

SERIAL DATA A

SERIAL DATA B

BUSY

CLOCK

CONVST

1/4

OPA4350

+5V

1/4

OPA4350

1/4

OPA4350

0.1

Serial

Interface

DGND

AGND

ADS7861

= 0V to 2.45V for 0V to 4.9V output.

Choose C

, C

to filter high frequency noise.

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: OPA2350

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: OPA2350