# Differences between Depletion and Enhancement MOSFET

A MOSFET(Metal Oxide Semiconductor Field Effect Transistor) is a three terminal semiconductor transistor. There are two types of MOSFET- depletion MOSFET(or D-MOSFET) and enhancement-MOSFET(E-MOSFET). Each of the two types is further divided by N-type and P-type, that is N-channel depletion MOSFET and P-channel depletion MOSEFT, N-channel enhancement MOSFET and P-channel enhancement  MOSEFT. The N-channel and P-channel MOSFETs differs in what type of material is used as substrate. If the substrate is N-type then an N-Channel MOSFET results and if the substate is P-Type then we have P-Channel MOSFET. Here we will explain the different between Depletion MOSFET and Enhancement MOSFET.

Depletion MOSFET Enhancement MOSFET
There is N-Channel There is NO N-Channel
Can be operated on both negative and positive gate voltage Can be operated with only positive gate voltage
Normally ON, when gate voltage is zero Normally OFF, when gate voltage is zero
Drain current is flowing whether gate to souce voltage($$V_{GS}$$) is positive or negative Drain current starts flowing when the gate to souce voltage($$V_{GS}$$) is greater than the threshold voltage($$V_{th}$$) is reached
Transfer curve is defined by Shockley’s equation Transfer curve is NOT defined by Shockley’s equation
Drain Current:
$$I_D = I_{DSS}(1-\frac{V_{GS}}{V_{GS(off)}})^2$$
Drain Current:
$$I_D = k(V_{GS}-V_{th})^2$$
where,$$k=\frac{I_{D(on)}}{(V_{GS(on)}-V_{th})^2}$$
Biasing Methods:
(1) Zero Gate Bias Depletion MOSFET
(2) Fixed Gate Bias Depletion MOSFET
(3) Self Bias Depletion MOSFET
(4) Voltage Divider Bias Depletion MOSFET
(5) Current-source bias Depletion MOSFET
Biasing Methods:
(1) Ohmic Region Biasing
(2) Fixed Gate Bias Enhancement MOSFET
(3) Drain Feedback Bias Enhancement MOSFET
(4) Voltage Divider Bias Enhancement MOSFET
N-channel D-MOSFET drain curve
E-channel D-MOSFET drain curve
N-channel D-MOSFET transfer curve
N-channel E-MOSFET transfer curve
N-channel D-MOSFET symbol
N-channel E-MOSFET symbol
Applications
- Used as RF amplifiers in high-frequency front-end communications circuits
Applications
- Used mainly as switches in both discrete and integrated circuits. In discrete circuits, it is mainly used as power switches and in integrated circuits it is used fir digital switching - sometimes used in Class-AB power amplifier - also used as front-end high-frequency RF amplifiers