How to simulate unit-gain-buffer use gain-boosting in Hspice

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Hello, everybody:

I have a question about simulate unit-gain-buffer use gain-boosting in Hspice.
My simulate condition is below:
1.in+ input 0V~1.8V pulse.
2.in- connect to vo+
3.probe vo+
4.vo+ is about 1.4V

I don't know why vo+ is 1.4V not 1.8V.
Is my connect error??

Thanks for your deeply help!!
 

Re: How to simulate unit-gain-buffer use gain-boosting in Hs

Please check M6, M8 Trs. in saturation,
and reduce Vdsat under each 0.2v.

Because, 0.4v loss is two Vdsats from OUT 1.4v
 

Re: How to simulate unit-gain-buffer use gain-boosting in Hs

Thanks for ipierre's response. Could you please tell me how to reduce vdsat of M6, M8 Trs. under each 0.2v.

PS. I try few days and can't redece vdsat.

Thanks for your help
 

Re: How to simulate unit-gain-buffer use gain-boosting in Hs

Generally, in order to reduce Vdsat,
the size of any transistor should be as large as possible.

Vdsat =( 2Id / Kp*(W/L) )^(1/2)

and, adding one-stage(rail to rail) in your amplifier may be recommended.

Regards,
iPierre

P.S. Folded Cascode is "bad Output Swing..."
 

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