100W DC servo amplifier circuit using Power MOSFET

This is DC servo amplifier circuit, OCL Output 100w, use MOSFET K134 + J49 or MOSFET J162 + K1058, Output 112W at Speaker 8Ω. Power Supply +56V/-56V 4A /Ch.

For those who want to profanities fun. This is 100W power MOSFET amplifier series be able to you for sure. And can have a most sound frequencies response. If You think that, I say the truth, then invite you to consider this Circuit and build as needed.

How it works

From a first circuit, will see that characteristics of the circuit is similar to the OP-AMP power circuit, by a positive input for the signal input enters, and has input for connecting a feedback signal.

The circuit-of-100-watt-dc-servo-amplifier-by-power-mosfet

The circuit diagram of  DC Servo Power Amplifier  using MOSFET

This circuit can work well, even at low frequencies alike DC signal. So, we may be called “DC Amplifier circuit”. Which can be applied in the servo amplifier as well.

The gain of this circuit depends on the R8/R7, From values in the circuit to has amplified rates equal to 22.   If there is an input signal size 1V,  then the output voltage is 22 V.

From Ohm’s law, we can calculate the power output equal :

Power = (ExE)/R
= 22 x 22 / 8
= 66.5W at load 8Ω.

or = 120W  at load 4Ω

So if you want to output 100W at load 8Ω. We will need to enter the input signal is not lower than 1.28V.

The transistor Q5 as constant current Circuits as the bias of output MOSFET. So it can be adjusted by adjusting VR1. It makes the circuits more good stability.

The VR1 should be chosen carefully so as CERMET.

At the gate of output, MOSFETs have a Zener diode to prevent the input signal is higher than 14V.  Because MOSFETs will be damaged.

Recommended: High MOSFET Power Amplifier

The MOSFET runaway thermal

The advantages of the MOSFET power amplifier circuit that we know very well is to prevent overload by itself.
– That is, when the over load, will higher the temperature of MOSFET but values resistance of the MOSFET then be higher. (In normal transistors, the resistance will decrease.) As a result, the current through the MOSFET lower
– If install the heat sink the appropriate size, then can be easily shorted output, by the MOSFET will not be damaged.
The most important factor, which will make circuits work to its full potential is the power supply Circuits. We suggest using the power supply separately, for each amplifiers. The advantage of this power, is that it helps reduce cross talk and low frequencies as well.

The transformer should be able to provide the current at secondary coil than 3 Amp and has voltage output at 40 Volt center trap as well.

How to build

To build, just equipment installation the proper circuit drawings. What care must be taken, is to install the output MOSFETS, do not short-circuit with the heat sink, strictly prohibited.


The PCB of 100 watt DC servo amplifier by Power MOSFET

This project needs to use the speaker protection circuit. Otherwise, your speaker may be damaged.

– When sure that everything is ok then try to supply to this circuits. Without connecting the speakers. But using the a voltmeter to measure the voltage at the speaker. It need to be no the voltage or zero volts, if is not show that the, Circuits failure at any point exactly.

– And most important, it should not be overlooked is the soldering, especially, Beginners usually soldering is not good enough.

– When pressure Have on center of R. Then, the next step is to adjust the Idle current for this circuit. Adjust only 35mA is enough.

For installation into a metal box, just like a typical high watt amplifier circuits. What needs to be careful, is to install ground, Because If do not need to be will make Have simple oscillator.

Remember, the ground of input and output circuit, should be on separate lines, and the ground at the same point for the PCB of this circuit, the input and output ground have separate neatly.

– The ground wire, especially output and the power supply, use a large, durable power more than 15A.

The input enters this circuit, the point is that we can use two AC input and DC input depending on the requirements, but usually, it is recommended AC Input is safer.

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I always try to make Electronics Learning Easy.

This Post Has 3 Comments

  1. Olá, excelente post. Mas tenho uma dúvida. Qual o valor do indutor L1 e quais os valores da bitola e de voltas?

    Sem esses valores fica inviável o projeto.

  2. Hi,

    L1 = 10 voltas de fio esmaltado AWG18 enrolado no proprio corpo do Resistor de 10 ohms 2 Watts.
    Se preferir pode enrolar separada do resistor, num diametro de 10mm.

    L1 = 10 turns enameled wire AWG 18 wrapped around the body’s own Resistor 10 ohms 2 Watts. If you prefer you can roll separate from the resistor, a diameter of 10mm.

    [ ]’s

  3. 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly. Please look
    into it and email me with a answer Please & Thanks.

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