I'd like to buffer the output of an operational amplifier using a source follower.
The operational amplifier produces a sinusoidal wave like this.
I would like to buffer this signal. To do that I use a source follower like that.
I tried a few things.
But I see only small signal at the input of the mosfet. And mosfet doesn't enters into saturation region. I tested this circuit seperately and it works fine on his own.
This is the seperate version of the source follower. I'd like to replace small signal sinusoidal wave with output of operational amplifier.
How should I bias the MOSFET using LTSpice simulation software?
Update : I added a voltage divider resistor network to the non-inverting input of operational amplifier.
The input signal is a triangle wave. It's frequency is about 2.7 kHz.
Actual input signal, the green one in simulation looks like this:
Source follower is as before
This time output of source follower looks fine.
Isn't the input voltage of the source follower is quite high? Shouldn't the input voltage be very small? E.g. 500 mV etc.
At first glance I used decoupling capacitors instead of non-inverting input of the operational amplifier.
As you'd see input and output waves are almost identical.
Biasing from op amp non-inverting input
This time hopefully I should be able to find the non-inverting input.
There is about 3.5 volt bias voltage on the output signal.
This time I removed the first decoupling capacitor at the gate of the source follower to be able to operate mosfet in saturation region.
Also this time, the output of the source follower looks fine to me.