What to do when the value of Vgs is unknown?

[suhas_shiv]

Value of Vgs

When designing, say, a current mirror, you find the value of R and W/L. But you have to know the value of Vgs for that. Usually, in any book, Vgs is assumed to be some value for a particular technology. How do you actually design if the approximate value of Vgs(for a particular technology) is not known( Vgs depends on biasing also)?

Thanks

 

[paulux]

Re: Value of Vgs

There is no general rule for designing Vgs and it depends on your application. In low Vdd application, you try to minimize Vgs. If it operates at saturation region, Vgs>=0.2V. Just an example, this absolutely depends on process technology

 

[jluhzw]

Re: Value of Vgs

I gree with paulux.there is no absolute way.It depends on your applications and your fab technology.

 

[xerxer]

Re: Value of Vgs

you may try to set up a simple circuit to simulation the vgs using hspice or pspice .
i think the method probobly help you to get you vgs .THis is just an advice