Variable resistor and capacitor in cmos technology

[hacksgen]

Hi friends,

How can we design a variable resistor and capacitor in cmos technology.i am talking about resistance of value between 30Mohms upto a 1 Gohm and cpacitance values between some hundred femto farads and few picofarads.

Please suggest possible ways about how this can be done.Any material in this regard would be useful.

Thanks.

 

[milkdragon]

For variable capacitor, a simple MOS cap can do it. Simply change the bias at gate, the overall capacitance will change according to the bias. Some other advance variable capacitor like accumulation mode is also good

In most cases variable resistor can be done by MOS working in triode region. Again, the resistance is determined by the votlage applied to the gate relative to the voltage at both source and drain. However, given the value you want, seems like it is kind of tough to get it.

 

[hacksgen]

i have looked at the method u suggested but the resistance i get is low.any other methods by which i can get resistance in Mohms range