The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> MOSFET to generate 1 M Ohm - 60 M Ohm resistance
https://designers-guide.org/forum/YaBB.pl?num=1155010648

Message started by avlsi on Aug 7^th, 2006, 9:17pm

Title: MOSFET to generate 1 M Ohm - 60 M Ohm resistance
Post by avlsi on Aug 7^th, 2006, 9:17pm

Hi all,

Is it possible to generate a resistance between 1 M Ohm - 60 M Ohm using a MOSFET structure. It should be linear. I tried with the architecture given in Ken Martin book( MOSFET - C filters) and also from prof. Tsividis papers. But I am not able to get a good linear resistor.

Help me out.

Thanks in advance.

Title: Re: MOSFET to generate 1 M Ohm - 60 M Ohm resistan
Post by vivkr on Aug 9^th, 2006, 11:45pm

Hi,

Where do you need to use these linear resistors and how linear do you need them to be?

I can think of the following few examples, although they are all a little different from each other in terms of context:

1. Large Ron (upto 100 MOhm) using CMOS: Vittoz et. al., JSSC, June '88 (High Performance, Crystal Osc..., Section IV)

2. Linear current division: Bult, Geelen, JSSC, Dec. '92(An Inherently Linear & Compact Current Division Technique)

3. Linear Gm: Gilbert, JSSC, Jan. '98, (The multi-tanh principle....); this is with BJTs but you can use MOS biased in weak inversion.

Hope this helps.

Regards
Vivek

Title: Re: MOSFET to generate 1 M Ohm - 60 M Ohm resistan
Post by avlsi on Aug 10^th, 2006, 6:39pm

Dear Vivek,

Its nice to hear from you. But I can set the Vds to 0.1 V,so it is not a problem with Vds. But since It is a wide range, I am not able to acheive V-I linearity . I want atleast 40% i.e., for v = 1 then I=1 ,lly for V=40 I=40,after that its not required.

I will go thru the papers u have suggested.

Thanks.
Avlsi.

Title: Re: MOSFET to generate 1 M Ohm - 60 M Ohm resistan
Post by loose-electron on Aug 10^th, 2006, 11:25pm

Could you post something on what you are trying to do with such a huge resistance?

As a general rule I never try to use anything larger than 200K-300K on a PCB, and probably not larger than 10-20K in a chip.

What are you trying to do?

thanks,
Jerry