Logic Gate using Transistor and Diode not working on Proteus
This is a NOT gate:







simulate this circuit &ndash; Schematic created using CircuitLab

When In is 0V, Out is 5V.

When In is 5V, Out is 0V.



To make an LED show the output state, you will need an LED driver.

Like this:







simulate this circuit

When LogicIn is 0V then the LED is off.

When LogicIn is 5V then the LED will light.



Now, combine the two.







simulate this circuit

When In is 0V, then the LED lights.

When In is 5V, then the LED will go out.