Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

One confusion of this paper, Opamp usage

Status
Not open for further replies.
G

GDF

Full Member level 3
Joined
Aug 11, 2005
Messages
175
Helped
2
Reputation
4
Reaction score
1
Trophy points
1,298
Activity points
2,895
Please follow this paper to Fig.10 and Fig.11.
I can't realize why the opamp is without buffer to implement
the filter. The resistor laod will degrade the DC gain, but I don't
see any buffer inside the opamp. Any body can tell me why?
Thanks,
 

For convenience to read, I attach the figure of this paper.
 

I can see that the Opamp is a two-stage type; the first stage being a telescopic cascode.

So, the gain of the 2nd stage is not critical and can be sacrificed for the sake of buffering

That's what I think
 

elbadry said:
I can see that the Opamp is a two-stage type; the first stage being a telescopic cascode.

So, the gain of the 2nd stage is not critical and can be sacrificed for the sake of buffering

That's what I think
Click to expand...
Why not use source follower be the buffer?
 

Because source followers suffer bad performance due to body-effect + they need high voltage ( swing will be within Vgs of transistor .. can be large for low suppliues ) whereas common source provides higher swing, no body effect
 

elbadry said:
Because source followers suffer bad performance due to body-effect + they need high voltage ( swing will be within Vgs of transistor .. can be large for low suppliues ) whereas common source provides higher swing, no body effect
Click to expand...
But if the feedback resistor make the gm*Rf less than one, it means the
gain of 2nd stage is small than one. What will happen? Or, it's not the usual
case?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top