Would the following circuits work? I keep thinking I need a mixture of ptype and ntype mosfet or npn and pnp transistor for a half h-bridge, but I keep seeing schematics with only ntype mosfets or npn transistors.

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My thoughts are: Case 1: In Q2, since the voltage at D with respect to S cannot be guaranteed to be a constant, the circuit's behaviour will vary. Case 2: Similarly, in Q2 the voltage at C with respect to C cannot be guaranteed to be a constant, therefore Ice will vary.

Is this correct? I've kept the schematics simple on purpose to understand it better. I will eventually turn it into a full h-bridge with flyback diodes.


1 Answer 1


You can make an H bridge with devices of all the same polarity.

However the problem comes with driving the control terminals. This is usually solved by using the switching action of the bridge itself to generate a 'bootstrap' rail. In the case of N-ch FETs, this would typically be 15v above the most positive power rail to drive the upper gates fully. Using P-ch for the upper devices avoids this (slight) complication.


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