Transistor Biasing

[BlackMelon]

Hello,

I'm trying to give a voltage Vb1 and Vb2 in the figure. What circuit topology do I have to use for this?

Thank You,
BlackMelon

 

[Harald Kapp]

Huh?
Any voltage source will do, even a simple resistive divider as the load by the gates is negligible to non-present.

Could you detail your idea a bit more?

 

[BlackMelon]

Huh?
Any voltage source will do, even a simple resistive divider as the load by the gates is negligible to non-present.

Could you detail your idea a bit more?

I am trying to design an op-amp with specifications shown in the pdf file. I can use any topologies I want. But I am allowed to use only one voltage source. Is there any techniques to bias that point?

PS. I think using voltage dividers might get me in trouble after this. Because I have to play with (W/L) ratio to have a specified gain, forcing me to change the resistors in the dividers for new Vgs too. Do you think so? Or is this already the easiest way to do?

 

[Harald Kapp]

Is there any techniques to bias that point?

You could use a MOSFET based voltage reference. But that's probably cracking a nut with a sledgehammer. The accuracy of a resistive divider is probably sufficient in this application.

Because I have to play with (W/L) ratio to have a specified gain, forcing me to change the resistors in the dividers for new Vgs too.

If you need to change VGS for whatever reason, any circuit you use wiil have to be adjusted, be it a resistive divider or a voltage reference circuit.
When you build the resistors from MOSFETs, you can scale them together with the other MOSFETs, that may (or may not - I'm not deep into your circuit) help lessen the workload.