# inverting amplifier

Discussion in 'Electronic Basics' started by smokie, Apr 1, 2005.

1. ### smokieGuest

what happens if you short the output on an inverting amplifier to its
inverting input?

2. ### Lord GarthGuest

Here's a place that will explain it to you:

http://www.williamson-labs.com/480_opam.htm

Your text indicates the feedback is zero ohms, drop that into the equation
for an inverting amp and get back to us.

3. ### John PopelishGuest

It is programmed to have zero voltage gain.

4. ### Bob EldredGuest

Gain from the input resistor becomes zero. But, it turns into a
non-inverting, unity gain amp relative to the plus input of the amp.
Inverting gain = Rf/Ri = 0/Ri = 0. Non-inverting gain = Rf/Ri + 1 = 0/Ri + 1
= +1.
Bob

5. ### Active8Guest

It always amazes me... the little things you can learn from the most
basic books and articles. Like... no one ever told me god created
PNP transitors. Is this more persecution, Dr. Laura, and how should
I smite them?

Seriously, I have a real basic book which wouldn't have taught me
much except that it has a chapter on components. Different types of
Rs, Cs, etc. Or there's my physics book that's short on words and
big on equations contrasted with an EE series (9 volumes) which
covers 1st year physics with more explanatory words. It just adds a
bit.

6. ### Rich GriseGuest

You get a zero-gain inverter. I saw one of these in use once, and
my engineer was baffled by it. "What the heck is a zero-gain inverter
for?" and you could almost see the question marks around his head
like in the cartoons.

It provides a virtual ground. I believe that the reason for doing
it that way has something to do with temperature compensation or
input offset current of the downstream devices.

Or, if you lift the non-inverting input, it's a voltage follower.

Cheers!
Rich

7. ### smokieGuest

Thank you everyone