This is the 200 watt MOSFET amplifier circuit on Class G with PCB. It is suitable for the PA system. Which it is a high end for all your working. You can read more feature:
– maximum RMS output power: 200 watts at load 8 ohms or 360 watts at the load 4 ohms.
– Frequency response range: 10Hz.-150kHz.
– Minimum Harmonic distortion: 0.008%.
How it works
The input signal is sent to C1 into the base of Q1 that is connected with Q2 as the differential amplifier circuit. Then, this signal is increased to the section 2 (Q3, Q4). Next, the signal is sent to the transistors driver(Q12, Q13), to drive the output transistors (Q15, Q16). Finally, the output signal is a drive to the loudspeaker.
Figure 1↓ 200 watt MOSFET Amplifier circuit
In lower signal range, both transistors Q14, Q15 will doesn’t works. But when is the peak signal rage,this signal is sent to D3, D4 to bias Q10, Q11 works. As a result, the mosfet Q14, Q17 also works. This cause the power supply 2 that have the higher voltage up to 100 volts to the amplifier section. This feature makes the peak signal aren’t trimmed like the general others amplifiers.
Here are the highlights of the class G amplifier. Because all transistors do not need to work hard all the time. So, Reduce energy loss and heat of the output power transistors better than the others high power amplifiers.
How to builds it
First of all,make the PCB as Figure 2 which is actual-size of Single-sided Copper PCB layout. Then, assemble the parts on the PCB as Figure 3 Should check carefully several times. Because this project have more details, If the error it would have been severely damaged.
Figure 2 the copper PCB layout
Next,screw the power transistors and power mosfet on the heat sink. By use of mica sheets and the silicone pad to aid cooling. It was attached to the heat sink, Tighten the screws firmly. Remmeber! Do not the body of transistor strictly short circuit to the heat sink.
When we finish assembling the project. Then,short circuit the input to the ground. Next,apply the power to the project. After that,measure current that flow through the positive of the 100 volts power supply. We should read maximum current about 20 mA. Then, measure current at the positive of the 40 volts supply and also have maximum current about 20 mA.
Use the voltmeter measure voltage between both base of Q11 and Q12, then adjust VR1 until read the voltage about 2.6-2.7volts.
Lastly,measure at the speaker terminal it must be zero only. Now this amplifiers ready to use.
The power supply
We should use the transformer minimum current 4 Amperes (per channel), and secondary coil must have center trap at 70 and 31 volts as Figure 4.
At the filter capacitors should connects the low capacitors to reduce the oscillation of circuit in high frequencies,we use about 0.033-0.1uF.
Caution! This project needs to use the speaker protection circuit. Otherwise, your speaker may be damaged.
Parts you will need
- T1 (70-31-0-31-70V)__4A./CH.
- D1, D2: BRIDGE Diode 25A 200V
- C1, C2: 8200uF 120V Electrolytic Capacitors
- C3, C4, C5, C6: 0.033uF 250V, Polyester Capacitor
- C7, C8: 10,000uF 50V, Electrolytic CapacitorsMOSFET Main Amplifer
- Q1, Q2, Q1: 2SA872 or similar
- Q3, Q4: BC648 or similar
- Q5, Q6, Q7, Q8: 2SD668 or similar
- Q9: BD139 or similar
- Q10: 2SC1775 or similar
- Q12: 2SD669 or similar
- Q13: 2SB649 or similar
- Q14: 2SK176 or similar
- Q15: 2SD551, 2SC2608 or similar
- Q16: 2SB681, 2SA1117 or similar
- Q17: 2SJ56 or similarC1, C6: 1uF 63V, Polyester Capacitor
C2: 100pF 63V____Polyester Capacitor
C3_______________0.1uF 63V____Polyester Capacitor
C4_______________22pF 63V____Polyester Capacitor
C5_______________220uF 50V___Electrolytic Capacitors
C7, C22__________75pF 63V_Polyester Capacitor
C8_______________100uF 25V___Electrolytic Capacitors
C9, C13__________1pF 63V_Polyester Capacitor
C10______________4pF 63V_Polyester Capacitor
C11______________0.22uF 63V_Polyester Capacitor
C12______________390pF 63V_Polyester Capacitor
C14, C21_________0.47uF 63V_Polyester Capacitor
C15, C16_________0.0022uF 63V_Polyester Capacitor
C17, C18_________100uF 250V___
D1, D2, D3________1N4148_______75V 150mA Diodes
D4, D6____________1N5403____400V 3A Diodes
D5________________ZD 15V____1W Zener diodes
R1________________470K___1/2W Resistors tolerance: 1%
R2________________2.2K___1/2W Resistors tolerance: 1%
R3________________12K___1/2W Resistors tolerance: 1%
R4________________33K___1/2W Resistors tolerance: 1%
R5, R6, R7, R15_____68K___1/2W Resistors tolerance: 1%
R17, R18___________68K___1/2W Resistors tolerance: 1%
R8_________________56 ohms ___1/2W Resistors tolerance: 1%
R9, R10____________1.8K___1/2W Resistors tolerance: 1%
R11________________10K___1/2W Resistors tolerance: 1%
R12________________2.7K___1/2W Resistors tolerance: 1%
R13, R16___________1.2K___1/2W Resistors tolerance: 1%
R14________________270 ohms___1/2W Resistors tolerance: 1%
R19, R30, R32_______100 ohms___1/2W Resistors tolerance: 1%
R20________________200 ohms___1/2W Resistors tolerance: 1%
R21, R27____________470 ohms___1/2W Resistors tolerance: 1%
R22, R26____________150 ohms___1/2W Resistors tolerance: 1%
R24, R35____________0.3 ohms___5W Resistors tolerance: 5%
R25, R28____________220 ohms___1/2W Resistors tolerance: 1%
R29, R34____________10K____1W_Resistors tolerance: 1%
R31_________________33 ohms__5W Resistors tolerance: 5%
R33_________________39K___1/2W Resistors tolerance: 1%
R36_________________47 ohms__5W Resistors tolerance: 5%
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