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H-Bridge Fundamentals

Design Considerations

When building the circuit, it is important to ensure that the wires you use, or the traces on the PCB, are the correct guage to handle the current required by the motors. You do not want to have the wires in your circuit to melt, causing a short circuit, or have a trace lift off a PCB, causing the circuit to become ineffective.

Try to keep the wires running from the circuit to the motors as short as possible, as this will be a source of RF noise. Also, twist the 2 wires together to help cut down on EM emissions.


There you have it, that is a basic guide to creating an h-bridge motor driver. If you have an questions, comments, or concerns, don’t hesitate to ask me.

A special thanks to all those who helped me with feedback while I was working on this article.


I am not liable for any damage that may be caused by using this circuit. Take care when building the circuit, so you do not make any mistakes that might lead to damage of the circuit, or personal injury. Safety first.

If you spot a mistake, please let me know!

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  1. darling
    darling December 21, 2017

    am using RFP30N06LE mosfet for pwm based heating coil giving pwm from arduino. 15v applied to drain and mosfet is heating fastly . when i calcute current thruogh coil is 0.8 amps and gate voltage is getting dropped …can you plz suggest me any chnages….????

    • Roger
      Roger December 21, 2017

      When you say that 15v is applied to the drain, do you mean that the drain is connected to the power supply, and the source is connected to the coil? If so, you’re using what’s known as a “high side” arrangement. In order to turn on the n-channel FET in that arrangement, you will need to supply it with a higher voltage than 15v in order to turn it on.

      Instead, try putting it on the “low side”, so the drain is connected to the coil, and the source is connected to ground. This way, you can turn it off by driving it to ground.

      You may want to also use a gate driver (either a dedicated chip, or a simple transistor ) to drive the FET, as the Arduino’s I/O pins may not be able to supply enough current to rapidly turn the FET fully on and off with PWM. This will also have the added benefit of bringing the lower Arduino voltage to the full supply voltage at the FET’s gate, ensuring it’s fully turning on and off.

      I suggest reading through the rest of the pages in this article (Specifically Page 4), as I explain FETs and their driving requirements in more detail.

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