What is the operation princip of the circuit in the picture

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guilinwxb

Joined: 19 Apr 2008
Posts: 19

12 Dec 2008 16:57 What is the operation princip of the circuit in the picture

Hi, all
There is a cascode feedback amp with a complementary transconductance stage as illustrated in the Fig, it is used for better tradeoff between noise performance and linearity at low power consumption.

Can anyone tell me about the operation principle of this circuit, or any link to talk about it ?
Thanks a lot!

[img][/img]

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rfsystem

Joined: 25 Feb 2002
Posts: 858
Helped: 96

12 Dec 2008 20:18 Re: What is the operation princip of the circuit in the pict

I think vbp and vbn are set so that the transconductance devices work in linear mode and convert pseudo-differential volatge into differential current. The R's and C's are only the external components to the transconductance stage.

This type is very unusal because the signal voltage range is limited to
Vdd-Vth,p-Vth,n

I known only the NMOS or PMOS only case which give
Vdd-Vth

guilinwxb

Joined: 19 Apr 2008
Posts: 19

15 Dec 2008 2:23 Re: What is the operation princip of the circuit in the pict

thanks rfsystem,
All device are on a chip, this circuit is operated at 1GHz, it is used as a LNA. The R's value effect the feedback so it effect the voltage gain. The C's effect the frequency.