Description:
The first stage of the amplifier is a differential amplifier based on transistors Q1 and Q2. Capacitor C8 is the input DC decoupler, R1 limits input current and capacitor C1 bypasses unwanted high frequencies. The second stage is the driver stage consisting of transistors Q3 and Q4. Output stage is a complementary push pull stage based on MOSFETs IRF530 and IRF9530.Output is coupled the speaker using the inductor L1. Network comprising of R15 and C5 is meant for noise reduction. Capacitors C6 and C7 are power supply filters. Preset R6 is meant for adjusting the quiscent current.
Mosfet Amplifier Circuit diagram.
Mosfet amplifier circuit - 50 watts
Notes:
- Assemble the circuit on a good quality PCB.
- Use +/-35V DC dual supply for powering the circuit.
- For L1 make 12turns of enamelled copper wire on a 1cm dia: plastic former.
- C6 and C7 must be rated 50V; other electrolytics can be 10 or 15V.
- Heat sink is necessary for the MOSFETs. A 8x4x4 inch finned Aluminium heat sink will do. There is no such thing as a heat sink that is too large.
I tried to build this circuit. No gain, just distortion. If I turn the input down to a bear minimum it sounds fine. My ear is 2 inches away! When i increase the input, nothing but distortion, no gain at all. Any help?
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