Enhancement vs Depletion Mode MOSFETs – Full Comparison

1. Core Definition (Conduction State at Zero Gate-Source Voltage)

1.1 Enhancement-Mode MOSFET (E-MOSFET)

When VGS = 0, no conductive channel exists, and the device is cut off with nearly zero drain current.

A gate-source voltage exceeding the threshold voltage VGS(th) must be applied to form a conductive channel and turn the device on.

N-channel enhancement MOSFET: Turns on when VGS is higher than positive threshold voltage
P-channel enhancement MOSFET: Turns on when VGS is lower than negative threshold voltage

1.2 Depletion-Mode MOSFET (D-MOSFET)

Ions are implanted into the channel during manufacturing. A permanent conductive channel already exists at VGS = 0, so the device conducts naturally without gate bias.

The channel is depleted by applying reverse gate voltage to switch the device off; its key parameter is pinch-off voltage VGS(off).

N-channel depletion MOSFET: Conducts at VGS=0; cuts off only when VGS drops below negative pinch-off voltage
P-channel depletion MOSFET: Conducts at VGS=0; cuts off only when VGS rises above positive pinch-off voltage

2. Key Parameter Comparison Table

Comparison Item	Enhancement-Mode MOSFET (E-MOS)	Depletion-Mode MOSFET (D-MOS)
Status at VGS=0	No channel, fully cut off	Built-in channel, fully conductive
Characteristic Voltage	Threshold voltage VGS(th)	Pinch-off voltage VGS(off) (negative for N-channel, positive for P-channel)
Operating Gate Voltage Range	Only single-polarity voltage enables conduction (positive bias for N-channel, negative bias for P-channel)	Supports positive, zero and negative gate bias, ultra-wide operating flexibility
Conduction Mechanism	Electric field enhances carriers to create a new channel	Pre-fabricated channel; reverse electric field depletes carriers to shut down conduction
Circuit Symbol	Dotted line between source and drain (no native channel)	Solid line between source and drain (native conductive channel)
Common Part Numbers	2N7002, IRF3205, silicon power MOSFETs, internal switches in MCUs	Small-signal devices: JFET, 3DJ6, 2SK series RF transistors
Typical Applications	Power switches, motor drivers, digital logic, inverters, BLDC motor drives	RF amplifiers, constant current sources, impedance matching, small-signal amplification

3. Practical Working Example of N-Channel MOSFETs (Most Widely Used)

N-Channel Enhancement-Mode MOSFET

VGS(th) = +2V

VGS = 0V: Cut off, drain current ID ≈ 0
VGS = 5V: Fully turned on, large drain current flows

N-Channel Depletion-Mode MOSFET

VGS(off) = -4V

VGS = 0V: Fully conductive, stable drain current output
VGS = -5V: Channel depleted, device cut off
VGS = +3V: Channel widens further, drain current increases significantly

4. Circuit & Application Differences

4.1 Enhancement-Mode MOSFET (Industry Standard Choice)

Simple control: Automatically cuts off when gate is floating or zero-biased, high safety margin
Straightforward driving circuit, no negative voltage supply required
Dominant solution for power MOSFETs, switching power supplies, motor drives and digital chips

4.2 Depletion-Mode MOSFET (For Analog & RF Circuits Only)

Operable at VGS=0 without extra bias circuitry
Ideal for constant-current loads, high-frequency amplifiers and RF low-noise amplifiers
Drawback: Remains conductive with zero gate bias; unsuitable for high-power switching circuits due to safety risks

5. Quick Identification via Schematic Symbols

Enhancement-mode: Dotted channel line between source and drain
Depletion-mode: Solid channel line between source and drain

6. One-Sentence Summary

Enhancement-mode MOSFET: Non-conductive with zero gate bias; turns on only with applied gate voltage (mainstream switching device)
Depletion-mode MOSFET: Conductive by default at zero gate bias; requires reverse gate voltage to turn off (specialized for analog & RF circuits)