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Design >> Analog Design >> problem with current mirror
https://designers-guide.org/forum/YaBB.pl?num=1248446068

Message started by icekalt on Jul 24^th, 2009, 7:34am

Title: problem with current mirror
Post by icekalt on Jul 24^th, 2009, 7:34am

Hello,

When i simulated the circuit below, the drain current of transistor M5 is not equal to 100uA. What is the problem here?

thx

Title: Re: problem with current mirror
Post by raja.cedt on Jul 24^th, 2009, 8:07am

hi,
please check vds of M5..i think the problem is because of less common mode voltage.if you have less vds then please increase input common mode voltage.

Thanks,
Rajasekhar.

Title: Re: problem with current mirror
Post by icekalt on Jul 24^th, 2009, 8:35am

raja.cedt wrote on Jul 24^th, 2009, 8:07am:

hi,
please check vds of M5..i think the problem is because of less common mode voltage.if you have less vds then please increase input common mode voltage.

Thanks,
Rajasekhar.

hello,

Vds is 1.17687nV.

Title: Re: problem with current mirror
Post by boe on Jul 24^th, 2009, 11:08am

icekalt wrote on Jul 24^th, 2009, 8:35am:

hello,

Vds is 1.17687nV.

Then the transistor is not in saturation and therefor, will not act as current source.
BOE

Title: Re: problem with current mirror
Post by raja.cedt on Jul 25^th, 2009, 1:08am

hi,
so please increase vds of the tail transistor (just increase the common mode voltage)

Thanks,
rajasekhar.