🚀 go-pugleaf

In article <Oct.7.14.29.39.1992.5036@clam.rutgers.edu> steuer@clam.rutgers.edu (robert Steuer) writes:
>From: steuer@clam.rutgers.edu (robert Steuer)
>Subject: Need Op-Amp Help.
>Date: 7 Oct 92 18:29:39 GMT
>I just finished an Electric Circuits Lab and one of the circuits
>involved an op-amp where the op-amp had its two bipolar power supply
>connections, and a signal generator was feeding a sine wave into the
>non-inverting input of the op-amp.  Then, a direct connection was made
>from the output to the inverting input and the gain was measured.  It
>was found that there was no change in the gain.  Then, the same
>circuit was used but instead of the piece of wire going from the
>output to the inverting input a 27k resistor was used and the gain
>remained the same although one would have thought it would
>decrease.(At least I did anyway!)  Is this because there was no second
>resistor that would normally have gone from the inverting input to
>ground?  That is all I can come up with because the formula to
>calculate gain is Afb=(Rf)/(R1) + 1 for closed loop gain.
>Can anyone verify that my assumption is correct or not?
>                                  Thanks, Rob
>-------------------------------------------------------------------------------
>| Robert Steuer               Internet: steuer@clam.rutgers.edu               |
>| Rutgers University          Amateur Radio: KF2EK@N3FOA.#EPA.PA.USA.NA       |
>-------------------------------------------------------------------------------
Yes, you are right, both are buffers, and having 27k resistor would 
compensate for the offset current if your source impedance was 27k. The gain 
of buffer is 1.

Peace and Prosperity!
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