What is Enhancement MOSFET ?
Enhancement MOSFET:
- In an Enhancement MOSFET, the channel between the source and drain is initially non-conductive or weakly conductive when no voltage is applied to the gate.
- An enhancement-type MOSFET requires a positive voltage on the gate to create an inversion layer or induce carriers in the channel, allowing current to flow.
- The threshold voltage for an enhancement MOSFET is positive, and the device is turned off when no voltage is applied to the gate.
What is Depletion MOSFET ?
Depletion MOSFET:
- In a Depletion MOSFET, the channel between the source and drain is naturally present even when no voltage is applied to the gate.
- A depletion-type MOSFET conducts by default, and applying a voltage to the gate creates a depletion region in the channel, reducing the current flow.
- The threshold voltage for a depletion MOSFET is negative, and the device is turned off by applying a positive voltage to the gate.
Difference between Enhancement MOSFET and Depletion MOSFET
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| Sr. No. | Parameter | Enhancement MOSFET | Depletion MOSFET |
|---|---|---|---|
| 1 | Operation | Requires a positive gate voltage to conduct | Conducts in its natural state and requires no gate voltage |
| 2 | Threshold Voltage | Positive threshold voltage required | Negative threshold voltage required |
| 3 | Conductivity | Normally off (non-conductive) in its natural state | Normally on (conductive) in its natural state |
| 4 | Applications | Widely used in digital circuits and CMOS technology | Less common in digital applications, more in analog circuits |
| 5 | Carrier Type | Majority carriers are electrons | Majority carriers are holes |
| 6 | Voltage Biasing | Commonly used in NMOS and PMOS transistors | Less commonly used in modern CMOS technology |
| 7 | Circuit Design | Requires additional circuitry for pull-up or pull-down resistors | Simplifies circuit design, may not require additional resistors |
| 8 | Symbol Representation | Usually represented with an arrow pointing away from the channel | Represented with an arrow pointing towards the channel |
| 9 | Voltage Level Compatibility | More compatible with positive voltage levels | More compatible with negative voltage levels |
| 10 | Current Flow | Requires a positive voltage to induce current flow | Current flows by default and decreases with negative gate voltage |
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