biasing for current mirror

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clarkkent

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hai, i am now facing a problem on biasing the mos into saturation region.
can anyone help me with it?
The problem is when i bias the NM1 into saturation region, the PM4 will fall back to linear region. And also the other way round...


thank you...
 


PM4 seems in saturation. NM1 seems on the edge of saturation (137>120 mV). maybe just an adjustment of the W/L ratios is required.
 
Braski said:
PM4 seems in saturation. NM1 seems on the edge of saturation (137>120 mV). maybe just an adjustment of the W/L ratios is required.
Click to expand...

Thnx.
but the problem now is when i change the w and l ratio of the PM4 and NM1, the VDS sat of both will increase too. What I want to do is to decrease the Vth of the PM4. Is there any way to do so?
 

clarkkent said:
Thnx.
but the problem now is when i change the w and l ratio of the PM4 and NM1, the VDS sat of both will increase too. What I want to do is to decrease the Vth of the PM4. Is there any way to do so?
Click to expand...

To reduce PM4 Vth connect its body to its source to eliminate body effect.
 

You can try inserting a series resistor from the source side of each N mos. That would be helpful.
 
thnx...
it was my mistake..
actually i should bias the m4 to linear region and m5 to subthreshold region. anywhere. thnx ya.
 

There is no m5 in your diagram... but it's good to know you got it to work. May I ask where you found this topology?
 

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