Harman Kardon AVR 7000, Service Manual

Page: 96 / 163

REV. A
Information furnished by Analog Devices is believed to be accurate and
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
µ
V. 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/
µ
s 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
AVR7000 harman/kardon
96