The OPA627.

Updated: 10 Jan 2001

CONTENTS.

Introduction.
Specs.
Fig a. Series feedback: THD versus level, various loads.
Fig b. Shunt feedback: THD versus level, various loads.

INTRODUCTION.

The OPA627 (Burr-Brown) is a very expensive opamp with excellent DC precision. But is it any good for audio? The answer is yes. Distortion is very low, though there are the usual problems with input common-mode distortion when series feedback is used.
The OP627 is a single opamp. No dual version is available. The OPA637 is a decompensated version only stable for gains of 5x or greater. SPECS.
Here are the vital statistics:
All typical values, for +/-15V supply rails.

Supply voltage +/-18V abs max
Output range +/-12.3V typ (1K load)
CM range +/-11.5V
en 5.2 nV/rtHz typ 1 kHz
in 30 fA/rtHz typ
Ibias +/-1 pA typ
Slew rate: 55V/us
Supply current 7 mA
Unity gain stable YES
Cost 1179p RS Jan 2001
Note VERY low current noise due to DIFET inputs

OP627 driving the usual loads at 5 Vrms.
Series feedback, gain= 3.2x

OP627 driving the usual loads at 5 Vrms.
Shunt feedback, gain= 2.2x but noise gain= 3.2x
Gen-mon trace shows distortion produced by the AP System 2 generator.