question in a JSSC paper

Dear all:

I am reading a paper whose title is "CMOS Analog Integrayed Circuits Based on Weak Inversion Operation" (JSSC, vol. sc-12, pp. 224-231, June 1977).
Please see Fig. 10 in the paper (attached file).

It said that as the amplitude of Vin increase, the average Vg of transistor T1 must decrease to keep average Id of T1 as a constant.
Can any one explain the circuit operation for me?

Thanks!!!
slchen

slchen said:

Dear all:

I am reading a paper whose title is "CMOS Analog Integrayed Circuits Based on Weak Inversion Operation" (JSSC, vol. sc-12, pp. 224-231, June 1977).
Please see Fig. 10 in the paper (attached file).

It said that as the amplitude of Vin increase, the average Vg of transistor T1 must decrease to keep average Id of T1 as a constant.
Can any one explain the circuit operation for me?

Thanks!!!
slchen

Added after 8 minutes:

Sorry!! Forgot to attach the paper.
Thanks a lot.

slchen

Click to expand...

hi slchen ,
the reason i think, if we first assume the dc of Vg is constant, and the transistor T1 carry more currents in positive half period than that in its dc voltage,and less in negative half period. if the increased average current is bigger than the decreased one, the transisotr's average current in the whole period is not a constant Id; to keep this constant Id, the dc of Vg must be lowered.

and why the increased average current is larger than the decreased one, i think, it is because the T1 is biased in weak region when oscillation doesn't build up. and when oscillation begins, the T1 may work in its saturation region, its current is related with (vg-vt)² in positive half period. so i think it is the reason.

maybe i'm wrong. by the way, i want to suggest you to read another jssc paper by vittoz, the paper talk about crystal oscillator design, i think you can find it, and i think it can benifit you for your understanding this problem.
good luck
jeff

Jeff:

Thanks for your explaination.
I will think about it based on your explaination.

Besides, is the paper you suggested "High-performance crystal oscillator circuits: theory and aplpication"?

Regards,
slchen

slchen said:

Jeff:

Thanks for your explaination.
I will think about it based on your explaination.

Besides, is the paper you suggested "High-performance crystal oscillator circuits: theory and aplpication"?

Regards,
slchen

Click to expand...

HI,
yes, it is very good reference paper for designing a low power crystal oscillator.
goodluck
jeff