Re: gEDA-user: problem to simulate an astable multivibrator with uA741 opamp

[John Doty <jpd@xxxxxxxxx>]

On Apr 15, 2009, at 6:47 AM, joseda wrote:

>
> I'm trying to simulate an astable multivibrator with ngspice, but  
> the graphic
> i get is odd.

...

> XU1 1 2 Vcc -Vcc 3 uA741
>

...

> The voltage drop below 400V what's the problem?!!
>

You have a node named "-Vcc". You haven't attached this node to  
anything outside the opamp. Presumably you intended to attach a  
negative power supply. The opamp model contains a current source  
attached to this node, so letting it float makes rather high voltages.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user