100 + 100 watt stereo amplifier board price list

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Complete Stereo Amplifier in Compact Size

Just Connect Transformer and it is ready to go.

The Big 4700uf x 4 Capacitors & GBU1010 Bridge Rectifier power supply On Board. 

input can be given from USB / Bluetooth player or Mobile phone or any type of CD / DVD / PC / Laptop / LCD LED TV.

• High Power  - 100 Watt per channel Dynamic output power with 4Ω speakers
• Low THD + N -   Less then 0.1%  Total Harmonic Distortion at Full power output.
• Power Supply  - 10 Amps Bridge Rectifier and filter capacitors, 
• PCB Size - 167 mm x 78 mm, Thickness - 1.6 mm, Copper - 35um
• Transformer Recommended  - use 24 0 24 VAC 5 - 8 Ampere Transformer.
• Standard Components - All components used are available online or at your local electronics store. 
• No SMD components used - Only through hole components used, making soldering and replacement hassle free.  
• Low cost  - This amplifier can be made in a fraction of cost compared to similar amplifiers available in market. 

                                                        CLICK HERE to download 200w Stereo  amplifier circuit diagram 

Left Channel Working is described below, the other channel works the same.

Power Supply Section - 

Power supply section consist of Bridge Rectifier D1 which rectifies AC coming from transformer, the rectifierd DC then filterd by Reservoir capacitors C19, C20, C21, C22.

DC output jack is provided to connect other amplifire boards for making multi channel Amps.

Input Stage

 Input stage works as a  transconductance amplifier (voltage in - current out).This stage consist of Long Tailed Pair (LTP) made of Q1 & Q2 working as differential amplifier.

Input signal received at the base of Q1 is amplified and sent to VAS from collector.

Negative feedback (NFB) received at the base of Q2 from output determines overall gain and balance of the amplifier. Current is supplied to the LTP by resistor R4.

Constant current source is made of Q18, R4,D3 which provided current to input pair.

In simple words input signal is amplified by the input pair Q1 & Q2 and sent to VAS for further amplification.

Voltage Amplification Stage (VAS)

As the name suggests, all the voltage gain of the amplifier is achieved in VA Stage.  

Signal received from input stage at the base of Q3 is  Voltage amplified and sent to the base of driver transistor Q5.Current is supplied to VAS by resistor R9 & R10.

Biasing circuit is made of transistor Q4, which works as voltage divider. With preset RV1, base current of output transistors can be precisely adjusted.

Important to note that the biasing transistor Q4 & driver transistor Q5 can be tied together for better thermal tracking.

In simple words signal received from input stage is amplified by Q3 & sent to output stage.

Output Stage ( OPS )This circuit has Class AB output stage, so each half of the signal is amplified by each  NPN and PNP output transistors.

Driver Transistors Q5 & Q6 work as buffers to prevent excessive loading of VAS and also provide input to the output transistor Q7 and Q8 respectively.

Output Topology is Complementary Feedback pair which has improved linearity and  better thermal tracking.

Zobel Network - made of R15 & C6, provides protection against high frequency oscillations.

In simple words signal received from VAS is given to the output transistors via driver transistors. Output transistors conduct high current to drive the speakers load. 

  Transistors 

• Q1, Q2, Q4 - BC546-547-548-549-550

• Q3, Q6          - BD140, MJE350, 2SA1220, 2SA1381

• Q5,                 - BD139, MJE340, 2SC2690, 2SC3503

• Q8                 - 2SC5200, TTC5200, 2SC5200N, NJW0281G, TIP35C

• Q7               - 2SA1943, TTA1943, 2SA1943N, NJW0302G, TIP36C

• D1 - GBU1010 GBU810 GBU8M or Similar  Bridge Rectifiers

* - Always use complementary NPN-PNP pairs.