[sdiy] transistor op-amp problems

[Benalog Electrotech]

Reduce the gain. Any input voltage below 1 diode drop Q3 plus the saturation EC voltage Q6 (~1v)is going to be non-ideal in this circuit.

Pick a lower gain that will allow you to input more than 2v without going above an expected output 12v.

On 25/05/2012, at 11:00 PM, Elain Klopke <functionofform at gmail.com> wrote:

> 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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