advantages of cascode structure..

[bcdeepak]

hello

i read that cascode structure has advantages on high reverse isolation and reducing the effect of Cgd

plz explain them, how are they possible??

can anyone give me some material on this?

thank you

deepak

 

[frankiebai]

The output node and input node not connect through Cgs because of the cascode transistor, so the miller effect of Cgs can be reduced.

 

[markjiang]

the swing between the terminal of Cgd is reduced. because the gain between the gate and the drain is becomed smaller than there is no cascode transistor.

 

[bcdeepak]

how does the gain between Cgd terminals decrease due to the cascode?

 

[kennyg]

Because the gain=gm_input*(1/gm_Cascode)
,this gain is small,
so the miller cap=gain*Cgd is small.