How to boost the amplitude of my VCO?

Dear all:

My VCO has amplitude of at least 1Vp-p without output buffer.....but after i connect the VCO to output buffer which is composed of source follower, the amplitude degraded to about 0.7Vp-p at some freq band....unfortunately, the amplitude of at least 0.8Vp-p is required.....how can i boost my amplitude of the buffer? I've tried many method to optimize my design(increase current, transistor scale, biasing point..., etc)

Plz help me, thanks a lot!

s follower act as -ve feed back to the ckt so , gain reduced , use differential amp using two transistor act as buffer if needed you can inc the gain.

Dear manish12:

Could you describe the use of differential amp as buffer in detail? Thx!

I have the same problem. Could you please Manish through more light on the differential amp. Could you provide a shematic of the circuit or a paper ?

Thanks in advance.

You can use this topology (not necessarily to use BJT?s).
The total gain of the buffer could be adjusted varying C2 or R4.
The output impedance is constant vs wideband frequency.

Is there any CMOS solution ?

Use this output buffer, eather diff or single ended one