What is the threshold voltage?

As an expert in the field of electronics and semiconductor physics, I can explain the concept of threshold voltage. In the context of electronic devices, particularly in the design and operation of transistors, the threshold voltage (Vth) is a critical parameter. It refers to the minimum voltage that must be applied to the gate of a field-effect transistor (FET) to invert the polarity of the channel and allow current to flow between the source and drain terminals. For a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), the threshold voltage is the gate-to-source voltage (Vgs) at which the channel begins to conduct. Below this voltage, the channel is considered to be "off" or non-conductive. Above this voltage, the channel is "on," and the device can amplify or switch signals. The threshold voltage is influenced by several factors, including the doping concentration of the substrate, the gate oxide thickness, and the work function difference between the gate and the semiconductor material. It is a crucial design parameter because it affects the device's power consumption, speed, and noise margins.

The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals.