REV. A

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reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

Dual Bipolar/JFET, Audio

Operational Amplifier

OP275*

PIN CONNECTIONS

8-Lead Narrow-Body SO

8-Lead Epoxy DIP

(S Suffix)

(P Suffix)

OP275

OUT A

–IN A

+IN A

V–

OUT B

–IN B

+IN B

V+

1

2

3

4

5

6

7

8

1

2

3

4

8

7

6

5

OP275

OUT B

–IN B

+IN B

V+

OUT A

–IN A

+IN A

V–

Improved dc performance is also provided with bias and offset

currents greatly reduced over purely bipolar designs. Input off-

set voltage is guaranteed at 1 mV and is typically less than

200

µV. This allows the OP275 to be used in many dc coupled

or summing applications without the need for special selections

or the added noise of additional offset adjustment circuitry.

The output is capable of driving 600

Ω loads to 10 V rms while

maintaining low distortion. THD + Noise at 3 V rms is a low

0.0006%.

The OP275 is specified over the extended industrial (–40

°C to

+85

°C) temperature range. OP275s are available in both plastic

DIP and SOIC-8 packages. SOIC-8 packages are available in

2500 piece reels. Many audio amplifiers are not offered in

SOIC-8 surface mount packages for a variety of reasons; how-

ever, the OP275 was designed so that it would offer full perfor-

mance in surface mount packaging.

GENERAL DESCRIPTION

The OP275 is the first amplifier to feature the Butler Amplifier

front-end. This new front-end design combines both bipolar

and JFET transistors to attain amplifiers with the accuracy and

low noise performance of bipolar transistors, and the speed and

sound quality of JFETs. Total Harmonic Distortion plus Noise

equals that of previous audio amplifiers, but at much lower sup-

ply currents.

A very low l/f corner of below 6 Hz maintains a flat noise density

response. Whether noise is measured at either 30 Hz or 1 kHz,

it is only 6 nV/

√Hz. The JFET portion of the input stage gives

the OP275 its high slew rates to keep distortion low, even when

large output swings are required, and the 22 V/

µs slew rate of

the OP275 is the fastest of any standard audio amplifier. Best of

all, this low noise and high speed are accomplished using less

than 5 mA of supply current, lower than any standard audio

amplifier.

*Protected by U.S. Patent No. 5,101,126.

© Analog Devices, Inc., 1995

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

FEATURES

Excellent Sonic Characteristics

Low Noise: 6 nV/

√Hz

Low Distortion: 0.0006%

High Slew Rate: 22 V/ s

Wide Bandwidth: 9 MHz

Low Supply Current: 5 mA

Low Offset Voltage: 1 mV

Low Offset Current: 2 nA

Unity Gain Stable

SOIC-8 Package

APPLICATIONS

High Performance Audio

Active Filters

Fast Amplifiers

Integrators