Figure 2 The circuit protects the load against reversed battery using an N-channel MOSFET. When A terminal is positive and B terminal is negative, the transistor’s internal diode D1 gets forward bias ...

A zener diode is like a normal silicon diode, where a forward biased diode will pass current with a ~1 volt drop. ... This circuit will clamp the voltage to a maximum of Vz, ...

In the circuit, the amplifier with the most positive output controls the negative feedback path via the forward biased diode in the amplifier output. It forms a simple unity gain path via R1 or R2, R3 ...

A tunnel diode amplifier circuit. ... There will be an odd-looking circuit that seems to make no sense at all, an amplifier formed from just a forward-biased diode and a couple of resistors.