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DC Analysis for Bias circuit

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wael_wael

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Hi everybody

could some one help me to find out DC analysis for the following circuit for
examble, VDD= vdsat9 + vdsat10 +vdsat16 +vgs9 (correct me if i am mistake) but i need it for each branch
thanks in advanced

best regards
 
Last edited by a moderator:

hi
you are mistake
M16 is current mirror so we have current of M16 so we have |Vgs9| and so we have PCS3 and vice versa if we have PCS3 we have ID9 and Vgs16.
regards
 

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    wael_wael

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VDD=vds9+vds10+vds16=vds16+vgs9
 

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    wael_wael

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Thank you so much, now more clear for me
but i have 1 q more
that if we look to first branch frome the left side we cane see that
vdd=vdsat12+vdsat13+vdsat18
1.5=0.065+0.065+0.05
could u explain to me that
with my regards
 

Hi
assume
Id=0.5*beta*(Vgs-Vt)^2 (saturation)
so if draw Id vs. Vds we can find that for Vds> Vds(sat)
Id is Constant.
so in sat. region for specific Id and Vgs we can have any Vds that Vds> Vds(sat).
so we don't know Vds but we know Id and Vgs of each Transistor.
so
I know current of M18 (Id18) then I know Vgs12
=> Vds18=Vdd-|Vgs12|

regards
 

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    wael_wael

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Thank u so much, you are very helpful, let me also thank our fourm also.

but i still have that equestion could u calculate the volts in the mentiond branch
thank you
regds
 

VDD=Vds12+Vds13+Vds18=vgs12+Vds18

If choose the voltege of PCAS PCS2 properly, we can make Vdsat12<Vds12 and Vdsat13<Vds13 to keep mosfets in saturation region.
 

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    wael_wael

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thank i hope i got it rite,
bcz 0.065+0.065+0.05=0.18
but i will consider the second part of equation
vdd=vds18+vgs12
regards

Added after 2 hours 37 minutes:

Hi
could some one help to calculate v in the branches
i will be thankful so much.
regards
 

wael_wael said:
0.065+0.065+0.05=0.18
Click to expand...
Hi
I think that you have a basic mistake.
how you find Vds12 and Vds13?
you can not find Vds12 nad Vds13.
as I told in sat. region for specific Id and Vgs we can have any Vds that Vds> Vds(sat).
so you must just use Vgs to find each voltage.
for example Vds18=Vdd-|Vgs12|
but VICM=vdd-|Vds9|
in this case we must have Vds9 or we must use simulator or this equation:
Id=0.5*beta*(Vgs-Vt)^2 * (1+lambda*Vds)

regards
 

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    wael_wael

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thank you so mush, i have no basic in this area
any way i am so chy from my question but better if i don't know ask some one.

so i got the values from the figure above you can see that, but i am not sure those values are VDS
thanx
regards
 

Hi
I don't know what are the numbers in figure. (may be W/L)
what is this figure?
regards
 

i am very sur the number is volt of Transistors, this one is Bias circuit for OTA
regds
 

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