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Current Mirror Output resistance waveform

frasheed

Hello,

I am testing and small current mirror circuit using spectre simulation. For DC analysis everything is working but for small signal AC analysis I am measuring the output resistance by running AC simulation but It's not giving me any results. As per my knowledge, Current mirror Output resistance is rout=1/(lambda*Id) so my equation for output resistance is (1 / IF("/I0/I_OUT")) and for anaylysis I have chosen "ac" and Sweep variable as frequency and I am sweeping it from 1 to 100Ghz. For simple current mirror It's not showing any wave form but for cascode current mirror its showing a wave form. Could anyone guide me where I am going wrong ?

Thanks

  • Andrew Beckett

    First of all, did you save the current through that pin? Currents don't get saved by default. Secondly, as this is an AC analysis, you may need to turn on the "useprobes" (save AC currents) option on the Options->Save All form.

    Check in the results browser to see that the current is actually there.

    Regards,

    Andrew.

  • frasheed

    Thanks for the hint, I just noticed that my source AC voltage was missing :D,

    Its working fine now 

  • reyan
    hii i need your help can i get ur email id .
    i have to find output impdance so, can you plz tell me how to find output impedance of current mirror circuit.

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