What is the difference between enhanced and depleted MOSFETs?

In the field of modern electronics, MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a critical device widely used in digital integrated circuits, analog circuits, and power circuits. Among them, enhanced and depleted MOSFETs are two common types, which have obvious differences in operating principles, characteristics, and applications.



1. Enhanced MOSFET

Enhanced MOSFET is an N-channel or P-channel MOSFET that is in the cutoff state without gate voltage. When gate voltage is applied to an enhanced MOSFET, a conductive channel is formed, allowing the device to conduct current. The main features include:

Positive gate voltage required: Enhanced MOSFETs require a forward voltage to be applied to the gate to form conductive channels.

High input impedance: Due to the lack of direct current flowing through the gate, enhanced MOSFETs have a high input impedance.

Widely used: In digital integrated circuits and most applications, enhanced MOSFETs are one of the most commonly used devices.

2. Depletion type MOSFET

Depleted MOSFETs are conductive without gate voltage, and when negative gate voltage is applied, a potential barrier is formed in the channel, causing it to cut off conduction. The characteristics of depletion type MOSFETs include:

Negative gate voltage required: Depleted MOSFETs require a negative voltage to be applied to the gate to achieve cutoff conduction.

Low input impedance: Due to the direct impact of current on the gate on the device's conduction state, depletion type MOSFETs typically have lower input impedance.

Suitable for certain specific applications: Depleted MOSFETs are typically used in special situations, such as power amplifiers and specific analog circuits.

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3. Summary of Differences

1. Different working conditions:

Enhanced MOSFET: requires forward gate voltage activation.

Depletion type MOSFET: It can conduct without gate voltage and requires negative gate voltage to cut off conduction.

2. Different input impedance:

Enhanced MOSFET: With high input impedance.

Depletion type MOSFET: has low input impedance.

3. Different application ranges:

Enhanced MOSFET: Commonly used in digital integrated circuits and most applications.

Depletion type MOSFET: Typically used for special applications such as power amplifiers.

Whether in digital circuit design or analog circuits, a deep understanding of their characteristics can help engineers better optimize system performance and ensure that the selected devices meet the requirements of specific applications.