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Design >> Analog Design >> Beta multiplier not working properly for transient analysis
https://designers-guide.org/forum/YaBB.pl?num=1279127141

Message started by kanu on Jul 14^th, 2010, 10:05am

Title: Beta multiplier not working properly for transient analysis
Post by kanu on Jul 14^th, 2010, 10:05am

Hi All,

I designed Beta Multiplier for pbias = 0.8 V and nbias = 0.4V at 1.0 V
supply for 90nm. While I get right values for the biases in dc
analysis, in transient anlaysis it gives different values. Could it be
that startup circuit is not working properly as the Vbiasp = 0.2V and
Vbiasn = 0.9 V in transient analysis ? If so, how should I go about
fixing it ? Also, I tried only multiplier circuit without any start up
circuit. Again I face the same problem. Or is it that pbias = 0.8 V
and nbias = 0.4V are not possible at 1.0 V ?

I will appreciate any help in this regard.

Regards,
Kanu

Title: Re: Beta multiplier not working properly for transient analysis
Post by raja.cedt on Jul 14^th, 2010, 8:13pm

hi,
please post the schematic if possible with the waveforms, in order to make sure that whether problem is because of start up or some thing else please remove start up and use intial condition. Now if your circuit is working well then stp ckt is the culprit.

Thanks,
Rajasekhar.

Title: Re: Beta multiplier not working properly for transient analysis
Post by kanu on Jul 14^th, 2010, 9:09pm

Hi Raja,

Thanks for your reply. I figured out that Beta Multiplier was not working properly at the first place. I was able to fix it. But I couldn't manage to design for Vbaisn = 0.4 and Vbiasp = 0.8 in the same circuit. So I decided to keep two bias circuits.

I have a question here again. Is there a way (like cascade structures or so.. which I can connect to Beta Multiplier's Vbaisn) to increase my Vbiasn from 0.2 to 0.4V. This will help me to do away with the second circuit.

Regards,
Kanu