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Design >> Analog Design >> How to determine the input value for 1st-order low pass OTA-C filter??
https://designers-guide.org/forum/YaBB.pl?num=1361675327

Message started by Jlim on Feb 23^rd, 2013, 7:08pm

Title: How to determine the input value for 1st-order low pass OTA-C filter??
Post by Jlim on Feb 23^rd, 2013, 7:08pm

hello,

How to determine the input value for ibias and Vin to generate the correct AC response???urgent!!!
Hope someone can help me~~~
Thanks :)

Title: Re: How to determine the input value for 1st-order low pass OTA-C filter??
Post by buddypoor on Feb 24^th, 2013, 2:48am

Jlim, I don`t understand your question.
The circuit was designed by YOU, right?
In this case, only you know about the chosen bias points and the necessary bias input voltages.
Or do you expect that we are simulating your circuit?

Title: Re: How to determine the input value for 1st-order low pass OTA-C filter??
Post by Jlim on Feb 24^th, 2013, 9:24pm

Because i have try a lot of value for Ibias and Vin input~~but i still cnt get the correct general AC response for low pass filter~~ :( :(
Can someone help me try to simulate this circuit and what value i should put??? :)

Title: Re: How to determine the input value for 1st-order low pass OTA-C filter??
Post by tzg6sa on Feb 25^th, 2013, 6:36am

If you don't get a meaningful AC response, then probably your operation point is incorrect. Check voltages and currents in the devices! Check that all transistors are in saturation!

Title: Re: How to determine the input value for 1st-order low pass OTA-C filter??
Post by Lex on Feb 25^th, 2013, 8:27am

Your ibias is not flowing into a current mirror... so the gate of NM3 and NM2 is floating.