How do I get a bias voltage?

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aryajur

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Bias voltage generation

I need to bias the bulk terminals of PMOS devices to a value lower than Vdd of the circuit. But if I use a resistor divider, the divider branch takes up a lot of current. If I increase the resistance values, they will take up a lot of area !
How do I get a bias voltage?
 

Bias voltage generation

The voltage pump is the best for biasing for the bulk terminal.
On the other hand , maybe the MOS bias is ok.
 

Re: Bias voltage generation

use series transistors?
 

Bias voltage generation

I agree with the latter.
 

Bias voltage generation

By the way,you can use self-bias.
 

Re: Bias voltage generation

Remember one thing, we cannot bias the bulk of the pmos lower than the VDD
because it will cause forward bias voltage between source and bulk and will cause the current from the source going into the bulk. And this will cause short circuit between source and drain because they are sharing the same bulk.
 

Re: Bias voltage generation

Ya I know about the forward bias thing, but since my transistors are in the subthreshold region I have to bias the bulk a little lower than Vdd to reduce the threshold voltage using Body Effect.
 

Re: Bias voltage generation

Thanks for the replies,
I used series diode connected transistors with a resistor. It worked fine !
Thanks
 

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