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.

How to eliminate noise in MOSFET?

Status
Not open for further replies.

zahrein

Full Member level 2
Joined
May 28, 2004
Messages
144
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
1,454
NOISE in MOSFET?

What are the two types of noise of MOSFET, how to eliminate them? (Thermal and Flicker). Thanks :D
 

gunturikishore

Full Member level 2
Joined
Aug 19, 2004
Messages
146
Helped
13
Reputation
26
Reaction score
6
Trophy points
1,298
Location
INDIA GANDHINAGAR
Activity points
1,362
Re: NOISE in MOSFET?

As far as I know abt the Flicker noise you can not eliminate it when you are operating at low frequencies on any semiconductor devices. Even its orgin is clear till date.There is a way to reduce by using PMOS instead of NMOS whwereever possible. And thrmal noise is present always you have no way to eliminate it except to increse your SNR to decresde the BER.

Added after 1 minutes:

I am wrong in my reply that the origin is not clear for Flicker noise.
 

zahrein

Full Member level 2
Joined
May 28, 2004
Messages
144
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
1,454
NOISE in MOSFET?

how does thermal noise and flicker noise exist?
 

skal81

Full Member level 2
Joined
Jan 19, 2005
Messages
121
Helped
38
Reputation
76
Reaction score
18
Trophy points
1,298
Activity points
1,478
Re: NOISE in MOSFET?

Flicker noise seems due to random trapping/detrapping of carriers near the Si/SiO2 interface. But the subject is still under active discussion.
Thermal noise origin is the same as for resistor: random movement of cariers due to thermal excitation.

As to suppress them:
- Flicker noise can be reduced in low frequency circuits (like audio) by using double sampling or chopping. See the excellent article by Enz and Temes 'Circuit techniques for reducing the effects of op-amp imperfections: autozeroing, correlated double sampling, and chopper stabilization'
- For thermal noise, you need to reduce it by circuit design consideration (as said by gunturikishore you need to increase the SNR)
Hopes it helps
regards
 

gunturikishore

Full Member level 2
Joined
Aug 19, 2004
Messages
146
Helped
13
Reputation
26
Reaction score
6
Trophy points
1,298
Location
INDIA GANDHINAGAR
Activity points
1,362
Re: NOISE in MOSFET?

As I said in my previous reply Flicker Noise is inevitable in any semiconductor device. But the advantage with it is that you can neglect this noise safely at higher frequencies may be above 10 K Hz. Being Flicker Noise proportinal to the 1/freq
its noise is considerable at low frequency. This is highly significant and can not be neglected at base band frequencies.

Themal Noise is due the random motion of the electrons in any material above absolute (not centigrade) zero temperature. THis is almost same at any frequency and its noise depends on the Bandwidth of the system under consideration. You can refer any Communication or Solid State Devices book for these noises.
 

TiwstedNeurons

Junior Member level 1
Joined
Jan 27, 2005
Messages
16
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
126
Re: NOISE in MOSFET?

It is hard to eliminate the flicker noise in low frequency applications. But some people believe that PMOS has lower flicker noise than NMOS. As the transistor dimension decreasing, this advantage of PMOS become not so obvious.
 

rockycheng

Member level 5
Joined
Feb 4, 2005
Messages
91
Helped
6
Reputation
12
Reaction score
2
Trophy points
1,288
Activity points
864
NOISE in MOSFET?

Flicker noise is inversely proportional to the transistor area.
 

Ravi Karadi

Newbie level 6
Joined
Jan 21, 2005
Messages
11
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
78
Re: NOISE in MOSFET?

flicker is 1/f noise. dominant at low frequencies
thermal is white noise. depends on frequency range
 

Karthikeya

Advanced Member level 4
Joined
Jan 9, 2005
Messages
103
Helped
9
Reputation
18
Reaction score
1
Trophy points
1,298
Activity points
989
Re: NOISE in MOSFET?

if u r using a NMOS diff amp then noise figure can be improved by having PMOS diff amp on top of NMOS with same cascode structure. Noise is inherent in all systems. we can only try to reduce it

regards
karthikeya
 

Vamsi Mocherla

Advanced Member level 1
Joined
Sep 6, 2004
Messages
469
Helped
72
Reputation
144
Reaction score
11
Trophy points
1,298
Activity points
5,136
Re: NOISE in MOSFET?

Definately going for a very big transistor area can reduce the flicker noise. But, do not blindly do so. Thermal noise is reduced by higher gm when referred to the input. So, the key for Low noise design is to go for big widths and modest lengths.
 

lastdance

Advanced Member level 4
Joined
Feb 1, 2005
Messages
104
Helped
18
Reputation
36
Reaction score
1
Trophy points
1,298
Location
Singapore
Activity points
1,251
Re: NOISE in MOSFET?

i do not agree with going for very big transistor, it's actually harmful for a low noise circuit since u r more susceptible to noise coupling now. How big is very big?
 

Vamsi Mocherla

Advanced Member level 1
Joined
Sep 6, 2004
Messages
469
Helped
72
Reputation
144
Reaction score
11
Trophy points
1,298
Activity points
5,136
Re: NOISE in MOSFET?

What has the size of a transistor to do with noise coupling?It has relation to the substrate and the no of contacts you put for that.
 

mady79

Member level 5
Joined
Mar 30, 2004
Messages
91
Helped
7
Reputation
14
Reaction score
1
Trophy points
1,288
Activity points
922
Re: NOISE in MOSFET?

Flicker noise although looks like a low frequency phenomenon,it's one of the major source of noise in High frequency applications .In RF Applications one can see large Area for the input transistor's .Any insights into Kick back noise if the area of the mosfet is large ??
 

alasliu

Junior Member level 1
Joined
Dec 11, 2005
Messages
15
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,350
NOISE in MOSFET?

flick noise is important at mixed-signal systemaliased around clock frequency.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top