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hoe to implement good Gm_c filter circuit ??

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andy2000a

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Q1: use nmos Cap or MIM cap ?

Q2: how to use constant_Gm circuit in Gm_C filter

Q3: for High freqency filter , only Gm_c filter can be select or not ??
why not use MOSFET_C / OTA_C filter

Q4: Gm_c filter how to design low "group delay" and "low noise"


a good book is "Hi frequency contiuouns time filter in digital CMOS"
have any good book talk about Gm_C filter ??

thank you
 

Hi andy2000a,

1 - I would prefer MIM due to higher linearity
2- The book from Ken Martin, "analog integrated circuit design" has a contant Gm bias in page 259.

4- for low "group delay" use Bessel type of filter and for low noise, usualy needs higher capacitor values (higher power).

The book from Ken Martin, "analog integrated circuit design" has a chapter 15 about Gm-C filters.

I hope this was helpfull.

Bastos
 

Hi
thank you , I have this book .. I will study it

thank you ..
 

:p
I got some question about gm-C filter
1. what's the difference between gm-C filter ,OTA-C filter and
gm-OTA-C Filter

2. What's the major drawback in gm-C filter?
Parasitic Capacitor?Linearilty?


Thanks !
 

GM-C

has all disadvantages but the only one; continious tuning.

Noise/DynamicRange is defined by cap size !

1. GM-C does not use full supply as swing
2. Is inherent nonlinear, best try is NMOS in linear with NPN cascode
3. Uses class A mode. Dc Power equal to maximum power

Alternative is RC with class AB Opamp and switched cap tuning
 

may be this helps:
**broken link removed**

for capacitors today MIM cap with vertical parallel plates can achieve both good capacity/um^2 (nearly 1 to 1.5 fF/um^2) and substrate decoupling useful for high frequency applications.
**broken link removed**

BEST!
 

1. MOS cap is area efficient than the MIM, but is limited by the working voltage and linearity.

2. Depend on your definition, OTA-C is believed to be the same as the gm-c.

3. there is a new book about high frequency filter.

Yichuang Sun, Design of high frequency integrated analogue filters, IEE press.
 

Can anybogy tell how to find cutoff frequency of gm_c filter. Do we have to consider internal parasitic capacitances to find cutoff frequency(I mean cutoff frequency in frequency response of filter)?
 

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