how to Bias 20 amplifier

[udave]

Want to bias 20 amplifiers, each drawing 200mA @ 5V; the gate voltage (vgg) controls the drain (vdd).

Questions are doing have 20 single power supply to bias the vgg and vdd individual, so how can do this? Again try to bias 20 individual amplifiers
The Vgg control the Vdd,
1. set the vgg at -2am then turn on the vdd @ 5V,
2. Looking way to connect 20 amplifiers with 2 power supplies, 1 for the vdd and 1 Vgg.
Please help.

 

[steve.hunch]

Can you please give a schematic for at least one amplifier. I cant understand a thing that you wrote here

 

[udave]

Sorry don’t have the schematic.
Just want to bias 20 amplifiers.
Want to control the vdd with one power supply and the vgg with 1 power supply too.
Don’t have 20 power supplies to bias all of them.

Question is how can bias the 20 amp with one power supply for vdd and 20 for the vgg.

 

[dr pepper]

I didnt get it either.
You talking about linear amps, or switching current amps?
Linear amps tend to just have a pot acting as an adjustable voltage divider from the amps power rails driving an emmiter follower or similar, then the dc is coupled to either the output stage, or the output stage drivers.

Need a drawing/schematic.

 

[lhademmor]

In a audio push-pull device :
The only way i can see You can do this is by attaching a optocoubler at each amp, where the transistor part is the bias part and the led part goes to Your second supply.

In a circuit with an ota amp or like (was it LM13081 ?) :
set the transistor part of the opto between power 1 and the bias pin.

If standard opamp with 2 bias pins put the transistor part over a 1M resistor from bias pin to bias pin.

If no hit, then please do a drawing.... even by hand will be ok .