Help me ! I need a document which has a part of calculating output impedance

[thanh]

Hi All !
I need a document which has a part of calculating output impedance of all kind of current mirror .
I read a such doc before . Perhaps I deleted it
I have searched it for 3 hours but not still found it yet . It seem to be a doc of a Australia university . Oh !I need doc of all university
Thanks !

 

[jan.didden]

I think you can just get it from the data sheet. Zout is basically change in Vout resulting from change in Iout; Zout = delta Vout/delta Iout . So look up the transistor data sheet graph of Ic versus Vce. The angle of the line (in the conduction area) is the Zout.

Example: see the attached for BC546, let's say Ib = 100uA. The graph goes through the points Ic = 25mA @ Vce = 4V and Ic = 30 mA @ Vce = 15V. Then Zout at that bias level is 11V / 5 mA = 2.2kOhms, right?

Jan Didden

 

[thanh]

Thanks ! Output impedance of current mirror is complexer than outptut impedance of tst . Because current mirro often include many tsts and resistors , diodes,