Vishay AN804 Data Sheet / Manual
Summary
Explore advanced N-Channel and P-Channel MOSFETs designed for reliable power control and switching applications. This manual provides expert guidance on optimizing high-side switch circuits by comparing performance metrics, detailing superior complementary pair configurations, and presenting critical circuit solutions like bootstrapping and level shifting. Essential reading for electrical engineers and hardware designers specializing in power electronics who need to minimize crossover current and maximize efficiency in complex motor and load control systems.
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AN804 Vishay Siliconix
P-Channel MOSFETs, the Best Choice for High-Side Switching
Historically, p-channel FETs were not considered as useful as their n-channel counterparts. The higher resistivity of p-type silicon, resulting from its lower carrier mobility, put it at a disadvantage compared to n-type silicon.
Switching Ground-Return Loads
Getting n-type performance out of p-type FETs has meant The principal application of the p-channel, enhancement- larger area geometries with correspondingly higher mode MOSPOWER FET is in switching power (or voltage) to inter-electrode capacitances. Consequently, a truly grounded (ground return) loads. complementary pair—a p-channel and an n-channel device that match in all parameters—is impossible.
To drive the FET properly, the gate voltage must be referenced to its source. For enhancement-mode MOSFETs, this gate potential is of the same polarity as the MOSFET’s drain
Yet, despite its shortcomings, the p-channel MOSFET
voltage. To turn on, the n-channel MOSFET requires a positive
performs a vital “high-side” switch task that the n-channel
gate-source voltage, whereas the p-channel MOSFET
simply cannot equal.
requires a negative gate-source potential.
Used as a high-side switch, a p-channel MOSFET in a During switching, a MOSFET’s source voltage must remain totem-pole arrangement with an n-channel MOSFET will fixed, as any variation will modulate the gate and thus simulate a high-current, high-power CMOS (complementary adversely affect performance. Figure 1 shows this MOS) arrangement. Although the p-channel MOSFET cannot degradation by comparing n-channel and p-channel MOSFET complement the n-channel in both on-resistance and high-side switching.
capacitance simultaneously, such combinations as the low-threshold p-channel TP0610 and the n-channel 2N7000 together offer outstanding performance as a complementary pair.
P-Channel N-Channel
VDD – ILr DS
VGG – Vth
Load Load
FIGURE 1. Comparing the Performance Between N-Channel and P-Channel Grounded-Load Switching
Document Number: 70611 www.vishay.com Fax Back 408-970-5600 10-Mar-97
Page Summary Contents For Vishay AN804 Data Sheet / Manual
Manual Details
| Brand | Vishay |
|---|---|
| Pages | 4 |
| File Size | 39.69 KB |
| Published | June 06, 2026 |
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Frequently Asked Questions
Why are p-channel MOSFETs needed for high-side switching applications?
P-channel MOSFETs are used as 'high-side' switches because they require a negative gate-source potential to turn on, which is necessary for this function.
How can I improve the n-channel MOSFET’s performance and switching speed?
Bootstrapping the MOSFET is useful for achieving short turn-on times of a few milliseconds. This technique must maintain specifications that match or exceed the supply voltage.
What is best practice to prevent excessive crossover current in complementary circuits?
Using a series resistor, such as R4, can dramatically reduce undesired crossover current during switching in low-power drivers.
Are p-channel and n-channel MOSFETs always usable as perfect complementary pairs?
No, achieving a truly matched or universal complementary pair is stated to be impossible due to device differences.