Question

What is the working principle of e-MOSFET?

Answer 1

The working principle of an e-MOSFET (enhancement-mode Metal-Oxide-Semiconductor Field-Effect Transistor) is based on the control of current between two terminals (drain and source) using an electric field created by a voltage applied to the gate terminal. Here's how it works, broken down simply:

Key Components:

1. Source (S): Where current enters the transistor.
   

1. Drain (D): Where current exits the transistor.
   

1. Gate (G): Controls the flow of current between the source and drain by creating an electric field.
   

1. Channel: A semiconductor region between the source and drain, which is normally non-conductive in e-MOSFET (in the absence of gate voltage).
   

   

Working Principle:

1. No Gate Voltage (V_GS = 0): In an e-MOSFET, when there is no voltage applied to the gate (or when the gate-source voltage, V_GS, is zero), the transistor remains "off". The channel between the source and drain doesn't conduct because it's depleted of charge carriers (electrons in N-channel or holes in P-channel).
   

  

1. Applying Positive Gate Voltage (V_GS > 0): When a positive voltage is applied to the gate, it attracts electrons (for N-channel) to the region under the gate. This creates a conductive channel between the source and drain, allowing current to flow from the source to the drain.
   

    - In this case, the channel is formed in such a way that current can only flow if the gate-source voltage is above a certain threshold (called the threshold voltage, V_th).
    - If V_GS is greater than V_th, the transistor is turned "on," and current can flow from the source to the drain.
  

1. Increasing Gate Voltage (V_GS > V_th): As V_GS increases, the channel becomes more conductive, allowing more current to flow. This is because a higher V_GS attracts more electrons into the channel (for N-channel MOSFETs) and reduces the resistance of the channel.
   

1. Cutoff Region: When V_GS is below V_th, the transistor remains off, and no current flows between the source and drain.
   

Summary:

In simple terms, the e-MOSFET works by using the voltage applied to the gate to control the formation of a conductive channel between the source and drain. If the gate voltage is high enough (above the threshold), the transistor conducts. If the gate voltage is low, it doesn't conduct. This ability to switch between conducting and non-conducting states is what makes the e-MOSFET useful in digital circuits like switches and amplifiers.