Re: gEDA-user: Simple LM741 Op-Amp Example

[Gabriel Paubert <paubert@xxxxxxx>]

On Sun, May 17, 2009 at 12:29:52AM -0400, Michael B Allen wrote:
> Hi,
> 
> I'm just paying around but I'm trying to do a simple LM741 Op-Amp
> simulation. Here is my schematic:
> 
>   http://207.192.69.113/~miallen/lm741.pdf
> 

It can't work, but I have difficulty guessing what you want to do.
If you want an inverting amplifier, you have to put a resistor in 
series with V2 (between V2 and the inverting inputof the opamp), 
and probably change the DC voltage of V2 to 1/2 V1.

IOW, the inverting input is used for the feedback, but if you connect
it to a voltage source with zero impedance, it can't do its work.

> If I blindly mess with resistor values I can get the simulation to
> actually complete but the input node isn't giving me a good SIN.
> 
> Is my voltage divider wrong? How do I get -4.5 and +4.5 to Vss and Vcc
> respectively?

By using 2 voltage sources of 4.5V in series and using the common point
as a reference? 

But it's not the root of the problem. Voltages are only differences
or potential between nodes. The node you use as a reference is arbitrary
(not in practice, but in a simulation).

	Regards,
	Gabriel


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