difference between n-channel FET vs p-channel FET
This page on n-channel FET vs p-channel FET mentions difference between n-channel FET and p-channel FET. Both N-channel and P-channel FETs are essential semiconductor devices used in electronic circuits for controlling current flow. Their operation principles are based on the modulation of the conductivity of a semiconductor channel through the application of an electric field at the gate terminal, with the key distinction being the type of majority charge carriers involved (electrons for N-channel and holes for P-channel). Following section compares both FET types with respect to their features, symbol and construction.
n-channel FET
An N-channel FET is a type of field-effect transistor where the conductivity of the device is controlled by the voltage applied to the gate terminal. It consists of a semiconductor material, typically silicon, with three terminals: source, drain, and gate. The conducting channel between the source and drain is formed by the flow of majority charge carriers, which are electrons in the case of an N-channel FET. When a positive voltage is applied to the gate relative to the source, it creates an electric field that attracts electrons, allowing them to flow from the source to the drain, thus enabling current conduction.
N-channel FETs are widely used in electronic circuits for various applications, such as amplifiers, switches, and digital logic circuits. They are commonly employed in high-side switching applications and circuits with positive voltage requirements.
As shown in figure-1, n-channel FET is constructed using a bar of N-type material into which a pair of P-type regions are diffused. Fig-1 also mentions circuit symbol of n-channel FET.
Following are the features of N-channel Junction FET(JFET):
• Current carriers are electrons in n-channel FET.
• Mobility of electrons is large.
• Input noise is low.
• Trans-conductance is large.
p-channel FET
A P-channel FET is another type of field-effect transistor where the conductivity of the device is controlled by the voltage applied to the gate terminal. Similar to the N-channel FET, it consists of three terminals: source, drain, and gate. However, in a P-channel FET, the conducting channel between the source and drain is formed by the flow of majority charge carriers known as "holes." When a negative voltage is applied to the gate relative to the source, it creates an electric field that attracts holes, allowing them to flow from the source to the drain, enabling current conduction.
P-channel FETs are also used in various electronic circuits, particularly in low-side switching applications and circuits with negative voltage requirements. They find applications in power management circuits, voltage regulators, and battery-powered devices.
Similar to n-channel FET, p-channel FET is constucted using a bar of P-type material into which a pair of N-type regions are diffused. Fig-2 mentions circuit symbol of p-channel FET.
Following are the features of P-channel Junction FET(JFET):
• Current carriers are holes in p-channel FET.
• Mobility of holes is poor.
• Input noise is large.
• Trans-conductance is small.
Following table compares n-channel versus p-channel FET types with respect to various features or characteristics.
| Features | n-channel FET | p-channel FET |
|---|---|---|
| Charge Carriers | Electrons | Holes |
| Majority Carrier | Electrons | Holes |
| Conductivity | Conducts when Vgs is positive | Conducts when Vgs is negative |
| Turn ON voltage | Positive | Negative |
| Switching Speed | Faster | Slower |
| Drain current direction | From drain to source | From source to drain |
| Voltage Handling | Typically used for positive voltage applications | Typically used for negative voltage applications |
| Gate Threshold Voltage | Typically has a lower (negative) gate threshold voltage | Typically has a higher (positive) gate threshold voltage |
| Cost | Generally lower | Generally higher |
| Heat dissipation | Less heat dissipation due to majority carrier being electrons | More heat dissipation due to majority carrier being holes |
| Noise sensitivity | Less sensitive to noise | More sensitive to noise |
Conclusion : Overall, from the comparison between n-channel FET and p-channel FET it is imperative that n-channel FET serves better than p-channel FET. The characteristics mentioned help engineers choose between n-channel and p-channel FETs or MOSFETs based on their specific application requirements, such as voltage polarity, switching speed, cost, noise sensitivity and thermal management.
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