1: Operation of a
conventional transistor
The metaloxidesemiconductor field-effect transistor (MOSFET) is the basic switching and amplification device of digital electronics. The current between the source and drain electrodes is controlled by the gate voltage. (a) When the gate voltage is zero, no conduction electrons are present in the channel. (b) When the gate is at a positive voltage, electrons from the source and drain accumulate in the area of the channel close to the gate. (c) As the gate voltage is increased further, the number of electrons in the channel increases until saturation is reached. The potential seen by the electrons is also shown along a line going from the gate to the channel. With no gate voltage, electrons in the channel experience a potential that is higher than the bias potential, shown by the dashed line (d). As the gate voltage increases, the potential in the channel gradually lowers and electrons accumulate there (ef).