constant gm circuit in 0.18um cmos process

[yantom]

Constant gm circuits assume that the I-V property of MOS transistor is square. But if i want to design a constant gm circuit which the channel length of the MOS transistor is 0.18um, the I-V property doesn't follow the square law, how do i design this circuit.

 

[khouly]

in analog design , u don't use the minimum channel lenght ,specially to design bias network and bandgap reffernce , most of the time , the length is about 5 times the minimum ad this make the transistor awy for short channel effects , and it is closely square law

khouly

 

[yantom]

But now i want to design a constant gm circuit for LNA, so i choose the minimum channel length.

 

[khouly]

also it will be used long devices , the bias circuit , will not pass RF singals , so it still can be long ,

so the LNA is not a factor in bias cell

khouly

 

[yantom]

you can ensure the MOS transistor of long channel length is constant gm, but if you mirror the current or the voltage, how can you ensure the MOS transistor of short channel length is constant gm. Their I-V cure is different