electronics-amplifier tutorial

A audio power amplifier circuit ideal for guitar or PA work or for use as a general-purpose subwoofer or hifi amplifier. Many people prefer Mosfets because of their legendary ruggedness. Altronics had a Mosfet amplifier module which produced 200W into a 4 Ohm load and so we decided to take a look it. It turned out to be based on the "Pro Series One" as mentioned above, although this version by Altronics has been derated and adapted to different Mosfets. It has a rated power output of 140W into 8W and 200W into 4 Ohm. Frequency response is within 1dB from 20Hz to 80kHz. Total harmonic distortion is rated at less than 0.1% up to full power and signal-to-noise ratio with respect to 200W is better than 100dB unweighted. 

This 200W MOSFET Amplifier  Circuit From http://electronics-diy.com/

Another design that uses the output transistor technology V-MOSFET. The transistors are we offer many advantages over a simple bipolar transistor, such as high speed, thermal stability, low distortion, etc.


The use of diodes D2 until D5 in combination with the resistances R17-19, they protect the gates of transistors v-fet from exceeds the voltage ± 14V and it creates perforation in very thin layer SiO2, that is used as insulation in the gate. This way of protection is common in all the amplifiers that use these transistors. The total gain of amplifier is 32.6, regulated from the R18, R6 and R8, in the negative feedback. Also is used enough the use of local feedback for stabilisation of operation under all the conditions. Because the transistors v-fet have positive factor of temperature, with result with the increase of temperature is increased also their resistance. This increase has as result the reduction of current that via the transistor, hence also his power. The use of separated supply in the stages of drive and exit, ensures stability and reject of distortion of intermodulation.

Series of VMOS FET POWER [ 2SK134 or 2SK135 ] [ 2SJ49 or 2SJ50 ], they are that, more above transistor they are not produced more by the Toshiba and are enough difficult they are found henceforth. They can be replaced with [ 2SK1530 in the place of 2SK135 ] and [ 2SJ201 in the place of 2SJ50 ]. The new transistors are in plastic case ΤΟ-3Ρ and no TO-3, bear in bigger supply of operation and have positive factor of temperature. This mean that with the increase of temperature, is increased and the current that is gone through from through the transistor. The new transistors him I have still not tryed and me it would interest to learn if somebody him used also with which results.

The following is a circuit of 25Watt High Quality power amplifier Mosfet IRF530-IRF9530 from Motorola's transistors are employed in the preceding stages. The supply rails prudentially voltage was kept at the rather low value of + and - 32V.

Skema Rangkaian 25Watt Audio Amplifier Mosfet

The following is a 60 - 90W High Quality power amplifier. Circuit topology is about the same of the above mentioned amplifier, but the extremely IRFP9240 Rugged IRFP240 MOSFET devices and are used as the output pair, and well Renowned high voltage Motorola's transistors are employed in the preceding stages. The supply rails prudentially voltage was kept at the rather low value of + and - 40V. For those wishing to experiment, the supply voltage rails could be raised to + and - 50V maximum, allowing the amplifier to approach the 100W into 8 Ohm target

Skema Rangkaian 60watt Amplifier Mosfet IRFP240-IRFP9240

Skema Rangkaian Mosfet Audio Amplifier

Daftar Component Audio Amplifier Mosfet

The transistors Q6 & Q7 should be fitted on a small and U-shaped heatsink while a larger heatsink is used to mount the transistors Q8 & Q9. For the regulation of voltage, the trimmer R10 is set to its minimum resistance which is made possible when powering ON the amplifier and then adjusting R10 until the drawing of the current reaches about 120 mA to 130 mA. If necessary, the current will need to be readjusted when after 15minutes, the current keeps on varying.

The circuit power supplay suggested value for capacitors C1 & C2 should be at the required minimum for a mono amplifier. The capacitance values may be increased up to 10000 uF when used in stereo configurations to achieved optimum performance. To eliminate ground loops and hums, an appropriate grounding is very essential. This will be done by connecting R1, R3, C2, C3, & C4 to the same point of the ground sides and the ground input wire while in the output ground, C7-C11 & R7 will be connected. Finally, the input and output grounds will be connected separately to the power supply ground.