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Currently I am doing a project on a voltage regulator. Can you tell me some advantages of MOSFETs over BJT? Apart from a higher power loss, I can not find much. In control engineering it is much more difficult to deal with them. Would be great if you could tell me a few.

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Please elaborate on 'much more difficult to deal with them'. To me, controlling a series-pass MOSFET gate voltage is trivially easy with an op-amp. – Adam Lawrence Aug 8 '14 at 15:26
to get stability with pmos is not as easy as it sounds. They start oscillating very easy. – Simon Aug 8 '14 at 15:43
Anything with a feedback loop can oscillate very easily. Also please update your question if you specifically want to consider PMOS / PNP. – Adam Lawrence Aug 8 '14 at 16:45

In a linear regulator, switching speed isn't a consideration. However, BJT base current can be. There's no steady-state gate current in a MOSFET so a MOSFET can be lower loss.

Also, a MOSFET in the on state looks resistive, so the dropout voltage can be very small at low currents. A BJT will saturate and may lead to higher dropout voltage at low currents.

At higher currents a BJT can suffer from low current gain.

All of these things can be mitigated by proper design, but they are definitely considerations when choosing a pass element.

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Just to add one downside of MOSFETS, if you want to use an N-Channel you have to have a way to bring the gate higher that the input voltage, and if you use a P-FET the area will be significantly larger than an N-FET or BJT for similar performance. – John D Aug 8 '14 at 15:34
that's true, so far I have not managed a pmos regulator to stabilize. They start pretty quickly oscillate at higher loads, despite snubber etc. – Simon Aug 8 '14 at 15:46
Sounds like you don't use appropriate compensation - BTW snubbers are used for suppressing high-frequency switching noise, not in regulator control loops. There's nothing inherently wrong with using a MOSFET as a regulator. – Adam Lawrence Aug 8 '14 at 16:47

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