[sdiy] transistor op-amp problems

Elain Klopke functionofform at gmail.com
Fri May 25 17:00:44 CEST 2012


Hey all,

I built the simple op-amp in the non-inverting amplifier setup shown
at the bottom of this page:
http://www.allaboutcircuits.com/vol_6/chpt_5/17.html

I used 2N3906s for the PNP transistors and 2N3904s for the NPNs and
put a 10Kohm reistor in the feedback loop and a 1Kohm resistor to
ground from the inverting input. In theory that should have produced a
gain of 11. However, when I adjust the pot so that one volt is going
into the non-inverting input of the circuit, I get 1.04 volts at the
output. I measured between the wiper of the pot and the ground
connection and between the output and ground. I can't quite figure it
out.

-Ian Smith


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