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small-signal simulation voltage gain

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mohazaga

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Hi,
I hope every body are ok , well I want to get small-signal simulation voltage gain .
So how we get it , is it by input AC voltage source (ampl=1 and phase=0) to my ckt and make AC sweep sim. ( set suitable freq. range ) then run the sim. and take the output voltage form ckt output.
i hope i explaine it clearly
thankx
 

pixel

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just like that
 

jjsnail

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that's open loop gain ,right?
 

mohazaga

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Hi ,
that is ok , but should I input some dc voltage ?
I mean , in sim. Vac =1 , phase=0 and vdc = ? .
should it 0 or some bias voltage . Beacuse when Vdc = some value not 0 , the Vo will change it's decrease , the max when vdc=0 ?
any body has answer
tahnkx
 

surianova

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mohazaga said:
Hi ,
that is ok , but should I input some dc voltage ?
I mean , in sim. Vac =1 , phase=0 and vdc = ? .
should it 0 or some bias voltage . Beacuse when Vdc = some value not 0 , the Vo will change it's decrease , the max when vdc=0 ?
any body has answer
tahnkx

you need to put Dc voltage to bias the transitor in saturation. If not, the
transistor will be off, u won't get any gain.
 

jinxingsun

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If you put op in the closed loop structure to make AC simulation,then you needn't have the DC value in the voltage source.
 

mohazaga

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HI ,,,
thanks for reply ,attached the sim. graph of the result , the Vdc varying from 0-1.6v where Vac =1 and AcPhase=0.
so , explain please
tahnkx
 

pixel

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Vdc should be set that mos is on and is in active region. If you set Vg below Vth mos will not work. Output dc level should be set in such way that enables high enough output voltage swing.
If you dont set dc operation points your ac simulation gives you a rubbish.
Can you post your schematic with voltage and current dc points.
 

mohazaga

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Hi,

I attach the schematic of the ckt.
thankx
 

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