[sdiy] Resistors in feedback loop of noninverting op amp buffer

[JH.]

Some early opamps like the infamous LM318 need such a resistor - says the 
data sheet.
(Probably to protect the input transistors from reverse current on 
overload?)

JH.


----- Original Message ----- 
From: "Aaron Lanterman" <lanterma at ece.gatech.edu>
To: "sdiy DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, November 22, 2008 8:18 AM
Subject: [sdiy] Resistors in feedback loop of noninverting op amp buffer


Every once in a while, I see something that's clearly a unity gain
noninverting op  buffer, but the designer has put a resistor in the
feedback loop. There's no resistor from the negative input terminal to
ground, so it's not like they're trying to provide gain. All the
textbooks show a wire from the output to the negative input terminal.

Why do people sometimes put a resistor there? When inputting
schematics into Eagle I keep wanting to just replace them with wires,
but I don't want to do that if there's a good reason they are there.

- Aaron
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