2 stage MOSFET amplifier

[augre]

Hi I am designing a two stage MOSFET amplifier.
The first stage is a Common-Source, the second is a Common-Drain (Source follower):
https://www.circuitlab.com/editor/#xb82e5

The circuit has to be output and input independent as much as possible. So as low magnitude error as possible at a source with non-trivial output R and for small loads.

I would like ideas on additional stages or changing something on the design to reach the most load independent result!

Thank you!

 

[crutschow]

What is the amp to be used for?

 

[BradtheRad]

I'm running a simulation of your schematic. Things are going well, it appears.

My observations:

1.

Your incoming signal has a certain amount of impedance. It would be appropriate to include an inline resistor as a way of indicating this impedance. Its value can be the maximum you expect under normal circumstances.

2.

If you attach a low resistance load, it will draw greater current at the output. In that case you will need to increase the capacitor value at the output, or else you will get reduced low frequency response.

 

[augre]

What is the amp to be used for?

Hi, it is only a school problem, nothing to be used for.

 

[crutschow]

You might want to bias M3's source output to be in the middle of the supply voltage. Thus the voltage divider output of R11 and R13 should be adjusted to a higher voltage, to include the Vgs threshold voltage of M3.

 

[augre]

You might want to bias M3's source output to be in the middle of the supply voltage. Thus the voltage divider output of R11 and R13 should be adjusted to a higher voltage, to include the Vgs threshold voltage of M3.

Thanks, I will try this.

Could somebody tell me about how the signal generator resistance affects the output?

If I add a resistor, even a 1 Ohm in series with the signal source the gain disappears at the output but the input signal magnitude doesn't change.

I don't understand this could you explain it?

- - - Updated - - -

Thanks, I will try this.

Could somebody tell me about how the signal generator resistance affects the output?

If I add a resistor, even a 1 Ohm in series with the signal source the gain disappears at the output but the input signal magnitude doesn't change.

I don't understand this could you explain it?

Sorry my simulation was wrong somehow the input resistance doesn't really affect it, i am very hangover messed up something probably.

- - - Updated - - -

Thanks, I will try this.

Could somebody tell me about how the signal generator resistance affects the output?

If I add a resistor, even a 1 Ohm in series with the signal source the gain disappears at the output but the input signal magnitude doesn't change.

I don't understand this could you explain it?

Sorry my simulation was wrong somehow the input resistance doesn't really affect it, i am very hangover messed up something probably.