Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic 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

What is the differences between Gm-C and SC filter?

Status
Not open for further replies.

byoungson

Newbie level 2
Joined
Apr 29, 2009
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,294
switched

What is the differences between Gm-C and SC filter?

I'm designing the Gm-C filter. But I don't know why I use this type of filter.

Could you explain about the differences?
 

LvW

Advanced Member level 5
Joined
May 7, 2008
Messages
5,819
Helped
1,738
Reputation
3,478
Reaction score
1,337
Trophy points
1,393
Location
Germany
Activity points
39,068
gm-c filter concept

1.) in gm-C filters a current source (OTA with its transfer gm) plays the role of an ohmic resistor (with the aim to create an RC time constant)
2.) in SC filters a periodically switched capacitor (loaded/deloaded via a fet switch) simulates the resistor functin.
 

byoungson

Newbie level 2
Joined
Apr 29, 2009
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,294
gm-c filter

Thanks. LvW

But I've already known about your answer.
The things that I wanna know are weak points about SC or Gm-C filter.

Why do people use SC filter, not Gm-C filter?
or opposite situation.

Could U reply? I really wanna know.
 

LvW

Advanced Member level 5
Joined
May 7, 2008
Messages
5,819
Helped
1,738
Reputation
3,478
Reaction score
1,337
Trophy points
1,393
Location
Germany
Activity points
39,068
It is not easy and not possible to give a final answer in short.
It really depends on your needs and on specific application conditions.
Both filters are suitable for integration purposes. Both offer the possibility for external tuning, but tuning the SC filter via the clock frequency is more linear and simpler as several time constants can be tuned at the same time.
But, of course, the disadvantage of the SC concept is the switched nature of the system with Nyquist limits and the necessity of pre- and after filtering.

Perhaps somebody else has some additional remarks.
Regards
 

eld03

Member level 2
Joined
Dec 29, 2007
Messages
46
Helped
5
Reputation
10
Reaction score
5
Trophy points
1,288
Activity points
1,505
lets be clear:
1. Gm/C filter has limited dynamic range.
2. Sability analysis in case of higher order gm/c filter would require analytical skills. Cad tools are of not use as breaking loop is guess work.
23. Gm/C filter is easy to design and control and used when your c is big in value so get R big by adjusting gm. low on silicon area.
4. Gm/C filter would be have higher noise ( double ended)

refer to gassiplex ASIC on web .
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top