The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
Subject: Re: SPICE and amp stability
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
X-Inktomi-Trace: public1-pete2-5-cust19.pete.broadband.ntl.com 1037862859 17586 188.8.131.52 (21 Nov 2002 07:14:19 GMT)
Date: Thu, 21 Nov 2002 07:14:15 -0000
NNTP-Posting-Date: Thu, 21 Nov 2002 07:14:20 GMT
Mike Engelhardt wrote:
>>>>> Or is there some more correct way to determine the loop
>>>> You have to look at the *loop* gain. This is the open loop gain
>>>> around the *feedback* path. This involves setting up a circuit such
>>>> that the opamp has a closed loop for dc (or very, very low
>>>> frequencies), but open loop for the main plot. This is so the amp
>>>> will bias correctly. The easist way to see how this is done is to
>>>> run my SuperSpice
>>> This is a poor way of doing this. All you have to do insert a
>>> floating AC voltage source in series with the feedback at in front
>>> of a high impedance point of the circuit, typically the opamp
>>> input. Then do your .AC analysis, and plot the ratio of complex
>>> voltages to either side of the voltage source. This method also is
>>> a good one for bench use, called either a frequency response
>>> analysis or Venable.
>> It is a method that is used very often and does indeed work
>> in practise, despite not being exact. A poor method would be
>> something that basically don't work.
> Well, don't take it personally, but I thought it was a poor
> suggestion because it's more complicated
It what way is it more complicated? It would seem that having to
instruct the simulator to do a division rather then just drag test
points would be simplar.
>(not even accounting
> for having to download that piece of junk product of yours
> you were trying to promote with your followup)
I do feel sorry for you Mike. Have you considerd getting some help?
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup