After improving the quality of power MOSFET transistors and reducing their price, a huge part of radio amateurs began to think about using these transistors in the output stages of amplifiers. And if, the first “field workers” sinned with some kind of blurryness, then with the development of the circuits and the devices themselves, the problem of sound quality began to gradually go away.
It should also be noted the undoubted advantages of field-effect transistors over bipolar ones:
1. PT can withstand noticeably large impulse loads, or rather overloads.
2. The absence of input currents, in some cases, makes it possible to significantly simplify the swinging cascades.
3. The parameters are less dependent on temperature, besides they have a large linear section of the transfer characteristic.
The amplifier is assembled on 1 pair of quasi-complementary output transistors IRFP250N (Dismantling) with asymmetric preliminary stages, the module is also equipped with a thermal stabilization and quiescent current control circuit.
When using 8 ohm acoustics, the supply voltage can be raised to 45-50V to obtain the equivalent power at 4 ohms.
The module is easy to set up and requires only setting the quiescent current, depending on the supply voltage. The optimal quiescent current of the output stage is 60-120mA, which is approximately equal to 100-200mA for the power supply of the module as a whole. To adjust the quiescent current, the input is shorted, the load is turned off, the ammeter is turned on in the gap of one of the supply arms and the required value is set using a trimming resistor on the board, after which a pause of 5-10 minutes is needed. to warm up the radiator. You should focus on the acceptable temperature of the radiator (+ margin for a closed case).
For passive cooling at a supply voltage close to the maximum, a radiator of at least 750 sq. cm is required
Subjectively, the amplifier was pleased with the sound quality, it can be used for any acoustics that is suitable in terms of power parameters and can be considered as an alternative to amplifiers on microcircuits.
The module can be recommended for building a high-quality power amplifier, as well as for getting acquainted with field-effect transistors at the output.