What is the purpose of the Load transistor in a TTL Logic NOT gate?
Compare these two circuits:







simulate this circuit &ndash; Schematic created using CircuitLab

In which one(s) do you think the meters VM1 and VM2 can be made to show a voltage other than V = 0 Volt ?

In circuit A the NMOS1 can conduct some current so that the voltage at "out" can increase. Then VM1 can show a voltage larger than 0 Volts.

I think that in circuit B there is no chance at all of the meter VM2 showing anything but V = 0 Volt. Do you agree?

Update

OP suggested this as a "fix"for circuit B to make it work again







simulate this circuit

Look carefully at the circuit, note how Drain-Source of NMOS3 and VM2 are in parallel with the battery. The battery is ideal, it outputs Vbat, no matter what. Can NMOS3 then still influence the voltage across VM2?

Also note how "out" is now directly connected to the battery, so what can we then say about the voltage at "out"?