Mosfet Amplifier Circuits

Posted on Feb 6, 2014

This article lists various types of audio amplifier circuits using Mosfet. We have tested all these circuits in our lab and we found all of them performing satisfactorily. The amplifier employs only one transistor and two MOSFETs and few resistors and capacitors in a shunt feedback scheme. This tiny circuit can can deliver a whopping 18Watts into 8

Mosfet Amplifier Circuits
Click here to download the full size of the above Circuit.

Ohm speaker or 30W into a 4 Ohm speaker. To get such a good performance and stability out of few components, a high quality well regulated DC power supply is necessary. This is very essential for reducing noise and getting a constant output power on varying loads. A good DC voltage regulator able of providing more than 2 Amps @ 40V can be used. You can expect such a power supply design very soon here in the power supply section. Assemble the board on a good quality PCB. Use a preamplifier board with tone control prior to this amplifier to get better performance. If you don`t want, then no problem because this amplifier circuit has enough punch with in it. The diagram shown here is of a 10W MOSFET audio amplifier circuit that requires only a single supply. Single rail supply is seldom used in Class-B power amplifiers. Anyway, for low power applications like this it`s quite fine. Actually I got this circuit from an old cassette player that is still working and I am publishing it as it is. The powers MOSFETs BD512 and BD522 are obsolete now and so you may use any other matching power MOSFETS instead of them. Transistors Q1 and Q2 is wired as a Darlington pair works as the preamplifier. Preset R3 controls the quiescent current while R2 provides feedback. Output is coupled to speaker through capacitor C4. Capacitor C5 is the power supply filter and C2 is the input DC decoupling capacitor. The first stage of the amplifier is a...

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