MOSFETs are a wonder of technology that keep evolving every year. They are especially useful in power supply applications, including chargers and computer power supplies. An example is this tiny but powerful Vishay SI7938DP-T1-GE3 dual MOSFET. It is slightly larger than your favorite SO-8 packaged 555 timer, yet it has design maximum limits of 60 A and 40 VDC.
Note: The question was selected from DigiKey’s social media feeds.
Figure 1: Opening image from the Vishay SI7938DP-T1-GE3 dual MOSFET datasheet.
DigiKey offerings of N-channel vs P-channel MOSFETs
While P-channel types are available, most of the MOSFETs are N-channel. Let’s look at the DigiKey offerings:
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Single MOSFETs: DigiKey has 18,204 active N-channel MOSFETs and only 3,757 are P-channel.
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MOSFET arrays sized 50 to 100 A: From the 166 active DigiKey offerings, only four P-channel (this includes the dual-packaged N and P channel types).
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We can also look at the availability of gate drivers. DigiKey has 1,464 active N-channel offerings while there are only nine active P-channel drivers.
Based on this data we see that N-channel MOSFETs are favored over P-channel. However, there is an old saying, “Horses for courses!” It reminds us that each circuit you design is unique. There are times when the P-channel MOSFET is the clear winner.
Why is the N-channel more popular?
Without looking at the specification, we already know that they generally perform better on the system level cost and performance scales. Recall that a MOSFET’s performance is measured in terms of:
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On resistance
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Drain to source voltage (maximum)
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Drain current
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Switching speed, including time on and time off
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Ability to dissipate heat
Secondary factors such as the cost and complexity of the drive circuitry are a consideration. For an introduction to MOSFET drivers, please refer to this article exploring an Arduino controlled H-bridge that drives a DC motor.
What is your favorite MOSFET?
This article wouldn’t be complete without an invitation to identify our favorite MOSFET. My pick is the Jellybean 2N7000 / 2N7002 logic level switch. The 2N7000 is 50-year-old part originally advertised as a MOSPOWER FETlington. This is a play on words referring to the MOSFET’s ability to stand in for a Darlington transistor.
Parting thoughts
We would love to hear about your circuit designs and why you selected a P-channel MOSFET. Also, be sure to identify your favorite MOSFET(s) in the comments section.
Best wishes,
APDahlen
About This Author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.