100 watts OTL amplifier circuit using transistor MJ15003-MJ15004

If you are looking for a 100-watt OTL amplifier circuit, For the job a small PA system, The news spread in the village or the sound system for the conference. I recommend this circuit, Because sound is very loud. When compared to other circuits at power are equal and very durable. because As Amp OTL do not eat your very expensive speakers certainly. But the speaker may sound a little annoying in the only turn it on.

In addition, also use parts number little , easily constructed, without any adjustment. and It’s not hard to find and buy this equipment or to use the equipment replaced easily. because we use all transistors.

Note : You can see Others amplifiers projects with PCB

How it works
Read about the advantages it so much. Let’s see the details on this circuit. Of the circuit to see that we use the first pair differential transistor is No.MPS9682, the pre drives section is the Q3 we use transistor no. 2SD357.
, and The set of dual drive are 2SD357 & 2SB527, for the power transistor we use No.MJ15003 matched pair No.MJ15004 So Trust has a full watt to 100 watts absolutely.

The Figure 1 is transistors amplifier of 100 watts

the power-supply-90v circuit
The Figure 2 is PCB layout.

In figure next, this circuit we use the power supply DC90 Volt at 5 Amp, The AC voltage is converted from AC 62V by Bridge diode rectifier to be DC voltage then later pass to the filter Capacitor as voltage to 90V by you should the capacitor not low than 10,000uF 100V

Build this circuit
In Figure 3 is a PCB layout and positioning devices. In creating this project, be sure that the soldering is completed. The polarity of the diodes, capacitors electrolyzed is correct or not?

For safety, always complete your circuit before attach your power to the circuit, you should remove the power transistor before, then attach probe of the voltmeter at point between R15,R16 If you are using a multimeter that is not auto-ranging, set it to the 100V range. then, add power source to this project , the voltage to must be between 40V to 50V. But if wrong of these shows, the circuit will not work correctly, To check the value of the equipment used to assemble the proper place for it or not.
Once you make sure it, so can be connected the MJ15003+MJ15004 in the circuit. However need to make sure that The installation of transistors on a piece of cooling heat sink, all that is good, do not loose, or short-circuit with a cooling strictly prohibited.
Then, the input power into the circuit again. Measure voltage is equal when do not connected the power transistors, then Input the signal from preamp tone controls or audio CD to hear a Sample voice, so the complete process of creating this project it.

Q1,Q2_______MPS9682 pnp transistor = the Replace Part are BC557,BC556, BC560

Q6__________MJ15003____NPN_POWER TRANSISTORS(20A,140V,250W)
2SC3856 = NPN Epitaxial Planar Transistor 15A 300V 130W Silicon Transistors

Q7__________MJ15004___PNP POWER TRANSISTORS(20A,140V,250W)
2SA1492 = PNP Epitaxial Planar Transistor 15A 300V 130W Silicon Transistors

R1,R8,R9_____10K__1/2W Resistor
R2,R7________50K__1/2W Resistor
R3___________27K__1/2W Resistor
R4___________1K___1/2W Resistor
R5___________4.7K__1/2W Resistor
R6___________120 ohm___1/2W Resistor
R10__________22K_____1/2W Resistor
R11__________2.7K____1/2W Resistor
R12__________5K_____1/2W Resistor
R13,R14______300 ohm____1W Resistor
R15,R16______0.5 ohm_____5W Resistor
R17__________10 ohm ____1W Resistor
C1,C4________10uF 50V _____ Electrolytic Capacitors
C2,C5________100uF 50V_____ Electrolytic Capacitors
C3___________47uF 50V_____ Electrolytic Capacitors
C6___________150pF 63V_____ Polyester Capacitor
C7___________0.022uF 63V____ Polyester Capacitor

For this project I created for my friend about 15 years ago. Now it also works well.
But when you will to try creating a new generation still problems to buy a transistor sure.
Special instructions from friend of mine. On the transistor MJ15003 & MJ15004. Shape To-03. Which is now hard to find.
So number used as 2SC5200 & 2SA1943
or 2SC3856 & 2SA1492
TO-03P, which has a simpler installation. And cheap too.
I hope that friends many happy this project. But do not forget about security. Check it carefully.


  1. muthukrishnan July 29, 2012
  2. shailendra July 31, 2012
  3. admin August 2, 2012
  4. admin August 2, 2012
  5. idea August 2, 2012
  6. Elvin August 14, 2012
  7. MOHINDER SINGH WAHI September 19, 2012
  8. admin May 16, 2013
  9. EDI HARYANTO July 29, 2013
  10. Andrew Smith October 17, 2013
  11. Andrew Smith October 18, 2013
  12. Prakit April 23, 2014

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