The MOS transistor is non conducting when? A. Zero source bias B. Zero threshold voltage C. Zero gate bias D. Zero drain bias

The correct answer is: A. Zero source bias.

A MOSFET (metal–oxide–semiconductor field-effect transistor) is a type of transistor that uses a metal oxide to control the flow of current between two semiconductor regions. The MOSFET is a three-terminal device, with the source, drain, and gate terminals. The source and drain terminals are connected to the semiconductor regions, and the gate terminal is connected to the metal oxide.

When a voltage is applied to the gate terminal, it creates an electric field that attracts or repels electrons in the semiconductor regions. This electric field can be used to control the flow of current between the source and drain terminals.

If there is no voltage applied to the gate terminal, then there is no electric field and no current will flow between the source and drain terminals. This is why the MOSFET is non-conducting when the source bias is zero.

The other options are incorrect because they all involve applying a voltage to the gate terminal. When a voltage is applied to the gate terminal, it creates an electric field that can be used to control the flow of current between the source and drain terminals. Therefore, the MOSFET will be conducting when any of the other options are true.