Re: gEDA-user: ideal op amps in gschem

[Dan McMahill <dan@xxxxxxxxxxxx>]

> so just for fun, now that we're on the topic of silly op-amp tricks....
> Here's a circuit which I came across inside some commercially sold 
> equipment.  The unit was not cheap (in terms of cost) and was not for 
> the consumer market.
>
> This is a little circuit with only an op-amp and 3 passives.  Can't get 
> more simple than that right?  Turns out that the designers of it had 
> some troubles understanding it.
>
> The answers (to an accurate enough degree for engineering calculations) 
> can be had in about 3 lines of hand analysis but I think it illustrates 
> nicely how one must be careful with those "ideal" op-amps.  It's also a 
> good case of where one shouldn't substitute a simulator (with a model 
> which may not capture important details) for thinking!
>
> Have fun.
>
> -Dan
>
>
> p.s.  hint:  The pin on the schematic is the only connection (other than 
> power and ground) to the rest of the circuit that this little gem was 
> found in.

In case anyone wants a bigger hint, here is the context in which that 
op-amp circuit was found.

-Dan

Attachment: opamp2.pdf
Description: Adobe PDF document