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Design >> Analog Design >> Noise of the MOSFET as transducer(sensor)
https://designers-guide.org/forum/YaBB.pl?num=1422183666

Message started by adie_N on Jan 25^th, 2015, 3:01am

Title: Noise of the MOSFET as transducer(sensor)
Post by adie_N on Jan 25^th, 2015, 3:01am

Hai!! Good day

I am using the MOSFET as transducer to attract the electrochemical potential in buffer pH solution. my concern is choose the size of transistor based on the operation current (I bias). The MOSFET is biased at constant current (Id) and constant voltage (Vds) by fixing the Vgs. By increase the width of MOSFET(L= constant), the current Id will increase. Therefore, the transconductance, gm will increase.

I am using a simple circuit to investigate the input noise at the Gate terminal and the output noise at drain terminal of MOSFET

Based on my understanding
The formula of the noise voltage source which series the gate terminal ;
Svg(f) = Kf/2u(Cox^2)WLf

Sid(f) = kf(Ids)/Cox(L^2)f

Increase the Width (W), the noise voltage source at gate terminal will be reduced. Unfortunately, the current noise (Sid) will increase as increase the drain current Id (width increase).

My question are;

(i) is it the way of my investigation is correct? I mean the schematic that I draw (attechement)? and, is there any better configuration or the best approach to investigate noise of single MOSFET at simulation level?

(ii) Using the MOSFET as transducer(sensor), what should I consider? increase the gm so that the Svg(f) reduce but the Sid(f) is increase or reduce the gm so that the Sid(f) reduce but Svg(f) increase?

Thanks
Adi

Title: Re: Noise of the MOSFET as transducer(sensor)
Post by raja.cedt on Jan 25^th, 2015, 8:59am

depends on how your sensing parameter impacted by the noise, if sensor is going to be connected the gate, then sensing voltage would be corrupted by the voltage noise hence that noise matters. If you are going to connect sensing current at the drain, then current noise will be interested...