My MOSFET collection mostly donated by visitor.
Fig. 1 My MOSFET collection mostly donated by visitor.


Test Power MOSFET Transistors, IGBTs Results, Observations

by Lewis Loflin


I have taken on a number of issues regarding the construction of H-Bridge motor controls and related topics. I designed a simple tri-state CMOS control circuit using two CD4093 ICs.

The idea was not to buy specialized devices. Just use basic transistors, etc.

The output drivers for the motor have been combinations of IGBTs, MOSFETs, and bipolar transistors. The idea was to operate motors at 12-volts, 24-volts, 36-volts, and 48-volts.

The results are as follows:

IGBTs at least those I own shouldn't be used. They have a high voltage drop (Vce ~2V) and are better used for higher voltage switching.

See Insulated Gate Bipolar Transistor IGBT Circuits and H-Bridge schematic with Darlington-IGBT Transistor Outputs.

For motor voltages below 15-volts use a use MOSFETs: IRF4905 for the p-channel and an IRFZ44N for the n-channel.

For voltages above 15-volts use the opto-coupler-Darlington transistor circuit for the p-channel and an IRFZ44N. See Driving Darlington Transistors with Optocouplers

The issue comes down to rDS(on) resistance. Use as low a values as possible. See the following two graphics:

High rDS waste power cause overheating.

Low rDS delivers the most power to the load.

Variable power supply used in test circuits and videos:
LM2575 Simple Switching Voltage Regulators

LM2575 Simple Switching Voltage Regulators YouTube Video


See From Basic Digital Circuits to H-Bridge Motor Controls.

Special thanks to Paul for the MOSFETs!

N-Channel MOSFET test setup on my workbench.
Fig. 2 N-Channel MOSFET test setup on my workbench.


N-Channel MOSFET test circuit diagram.
Fig. 3 N-Channel MOSFET test circuit diagram.


In Fig. 3 the LM2575 Simple Switching Voltage Regulator replaced the 10K pot. This must connected to its own separate supply such as a cheap plug in the wall power supply. Observe polarity. Positive to gate negative to ground.

N-Channel MOSFET voltage values.
Fig. 3b


Observation: low rDS(on) MOSFETs are low voltage in general 55-60 volts. For higher voltage we often have higher rDS(on).

Many of the devices are easy to parallel but be aware gate-source capacitance, etc. add together.

P-Channel MOSFET test setup on my workbench.
Fig. 4 P-Channel MOSFET test setup on my workbench.


P-Channel MOSFET test circuit diagram.
Fig. 5 P-Channel MOSFET test circuit diagram.


In Fig. 5 the LM2575 Simple Switching Voltage Regulator replaced the 10K pot. This must be connected to its own separate supply such as a cheap plug in the wall power supply. Observe polarity. Negative to gate positive to ground.

Four IRF9630 MOSFETs in parallel.
Fig. 6 Four IRF9630 MOSFETs in parallel.


P-channel MOSFETs like n-channel can be paralleled for low rDS(on) as shown above.

P-channel MOSFET and IGBT voltage values.
Fig. 6b


Test Values P-channel MOSFETs IGBTs

Because I could use the same test setup for IGBTs as n-channel MOSFETs I tested those I had.

Conclusion: IGBTs don't work directly with 3.3V and 5V micro-controllers such as Arduino. At least 7-volts is required for turn on. The high Vce of 1.5V to 2V can waste power.

IGBTs do differ from MOSFETs with both positive flow and electron flow could deliver more power even at 2V Vce to the load. They are really designed for high-voltage switching.

* from spec sheet.
** no data found.

Also see Insulated Gate Bipolar Transistor IGBT Circuits Tutorial.

Download graphic mosfet_test2.jpg



Comparison IGBT, MOSFET, bipolar transistor current flow.
Fig. 7 Comparison IGBT, MOSFET, bipolar transistor current flow.


As shown in Fig. 7 MOSFETs are electron flow only devices only.

N-channel MOSFET turned off.
Fig. 8 N-channel MOSFET turned off.


N-channel MOSFET turned on.
Fig. 9 N-channel MOSFET turned on.



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