data books, PMI

Tony Allgood oakley at
Mon May 4 23:01:13 CEST 1998

Scott wrote:
Ever hear of the OP-27 (low noise, high speed, hi preceision opamp)? I was
a co-designer on that, and the metal mask still has my initials on it. I
use OP-27's instead of 741's because I had 150 or so of them from a
pre-production run (only about 50 left).

Well I did this in a variety of applications... but in some cases, the swap
really causes more troubles. If the OP-27 is used as a voltage follower,
then don't take the input too near the supply line because you will have a
very nice 1MHz oscillator. Took me ages to find the source of that. The
follower drove a 3080 VCA to control the ADSR envelope amount. But this 1MHz
was everywhere, audio outs, CV and even the so-called ground line. Another
time was in a tracking PSU. I had a good old 723 running the positive at
15volts, and a 741 op-amp driving a pass transistor to give the minus.
Replaced the 741 with a OP-27... and honk city. Sometimes you just can't get
slow enough.


Tony Allgood, Cumbria, UK

e-mail: oakley at

My latest project; a rack mounted VCF module with warmth. PCB arriving soon.

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