# Phase inverter

Discussion in 'Homework Help' started by kbcheong, Apr 7, 2012.

1. ### kbcheong Thread Starter New Member

Mar 24, 2012
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0

This circuit has 2 MOSFETS. The input signal is presented to the gate of Q1. Q2, is a two terminal device with its gate connected to its drain, is used as a replacement for the load resistor in a common source amplifier.

Assume that the MOSFETS is identical, with parameters K and VT.

We want to set the input bias VIN high enough to keep Q1 out of cutoff. If we want to be able to swing the input voltage up and down by Dv, what is the minimum value for the input bias voltage? How to define an algebraic expression involving Dv and VT for the minimum value of VIN?

What is the minimum value that the power supply voltage VDD must be to ensure both transistors are operating in the saturated region? How to define an algebraic expression involving VIN and VT for this minimum value of VDD ?

2. ### Audioguru New Member

Dec 20, 2007
9,411
896
You want Q2 to be a constant current source but instead it will be a constant voltage source.

I think that Q2 will try to hold the output voltage at a certain level.
When the output voltage tries to drop when Q1 conducts more current then it will pull down the source voltage of Q2 which will cause it to conduct more current. Then the output voltage will barely change.