The purpose of a 100 Watt Transistor Audio Amplifier Circuit is to transform a weak electrical signal from an audio source such as a phone or MP3 player into a considerably stronger signal that can power loudspeakers.
In this circuit transistors play the vital role to amplify the input signal into a massive 100 watt output signal.
Circuit Working:
Parts List:
| Category | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 4.7k | 1 | 1/4W |
| 680Ω | 2 | 1/4W | |
| 47k | 2 | 1/4W | |
| 10k | 2 | 1/4W | |
| 22Ω | 1 | 1/4W | |
| 22Ω | 2 | 1/2W | |
| 1k | 1 | 1W | |
| 1.5k | 1 | 2W | |
| 100Ω | 2 | 2W | |
| 1Ω | 2 | 5W | |
| Capacitors | Ceramic 560pF | 1 | |
| Electrolytic 1μF 50V | 1 | ||
| Electrolytic 4.7μF 50V | 1 | ||
| Electrolytic 10μF 50V | 1 | ||
| Electrolytic 47μF 50V | 1 | ||
| Semiconductors | BJT BC108 | 2 | |
| BJT 2N6107 | 2 | ||
| BJT 2N3773 | 2 | ||
| BJT 2N5294 | 1 | ||
| Miscellaneous | Loudspeaker | 1 |
The weak input signal is amplified in this first step.
This sections main components are resistors, capacitors and transistors Q1 and Q2.
The output of the preamplifier is further amplified for greater power in this intermediate stage.
To do this resistors like R8, R15 for Q1 and the resistors R9, R10, R11, R12, and R13 for Q2 collaborate with transistors Q4 and Q6.
The amplified signal is transferred to the loudspeaker in the last stage, which is represented by transistors Q5 and Q7.
Because loudspeakers have a very low impedance and the amplifiers output has a large impedance, this stage is critical.
By matching the impedances the driver stage makes sure the loudspeaker is not overwhelmed or harmed.
The total circuit has the capacity to produce 100 watts of electricity at its highest output.
The power source for the amplifier is dual polarity, which means that it provides both positive and negative voltage.
This power supply usual voltage range is 35V.
Formulas:
When designing a circuit for a 100 Watt audio amplifier that uses discrete components, such transistors there are a number of things to take into account, including transistor ratings, heat management and performance and stability assurance.
Here are the essential formulas for such a circuit:
Calculating Output Power:
With the following formula, one may estimate the output power Pout:
Pout = Vpeak2/(2 *RL )
where,
- Vpeak is the swing in the peak output voltage, and L is the load impedance (speaker).
- With a 35V power supply, the maximum output voltage can be nearly equal to 35V−Vsat, where Vsat is the output transistors saturation value.
Power Loss:
Determine the proper needs for heatsinks by calculating the power dissipation of each transistor:
Pdiss = VCE × IC
where,
- The collector emitter voltage is VCE, while the collector current is IC.
For a reliable 100 Watt audio amplifier circuit, it would be helpful to consult thorough amplifier design literature and perhaps an electronics engineer due to the complexity and particular requirements.
How to Build:
To build a 100 Watt Audio Amplifier Circuit using Transistors follow the below mentioned connections steps:
- Assemble all the components mentioned in the above circuit diagram.
- Connect collector of transistor Q1 to positive supply of +35V through resistor R, connect base of transistor Q1 to audio input through capacitor C1,connect emitter of transistor Q1 to emitter of transistor Q2.
- Connect collector of transistor Q2 to positive supply of +35V, connect base of transistor Q2 to resistor R6, connect emitter of transistor Q2 to -35V through resistors R3 and R4.
- Connect base of transistor Q3 to one end of capacitor C5, connect collector of transistor Q3 to the base of transistor Q4, connect emitter of transistor Q3 to +35V.
- Connect base of transistor Q4 to emitter of transistor Q3, connect collector of transistor Q4 to positive supply of +35V, connect emitter to the base of transistor Q5.
- Connect base of transistor Q5 to emitter of transistor Q4, connect collector of transistor Q5 to positive supply of +35V, connect emitter of transistor Q5 to loudspeaker through resistor R16.
- Connect base of transistor Q6 to resistor R10 and R11, connect collector of transistor Q6 to base of transistor Q7 and emitter of transistor to resistor R15.
- Connect transistor Q7 base to collector of transistor Q6, connect collector of transistor Q7 to loudspeaker, and connect emitter of transistor Q7 to -35V through resistor R14.
- Connect resistor R5 and capacitor C3 from base of transistor Q2 to ground, connect capacitor C2 positive end between resistor R3 and R4 and negative end to the ground capacitor C3
- Connect resistor R8 from positive through diodes D1 and D2 to between resistors R9 and R10.
Safety Measures:
- Make sure you have the right soldering equipment.
- A 100 watt amplifiers transistors produce a lot of heat.
- To avoid overheating and component damage, use the suitable heat sinks with the right thermal paste.
- Start testing at a low volume and work your way up while keeping an eye out for any anomalies in the circuit.
- Make sure all of your wiring and component placement are correct before turning the circuit on to prevent mistakes or shorts.
Conclusion:
To conclude, a 100 watt transistor amplifier boosts weak audio signals through three stages: voltage gain, driver, and pre amp.
It generates heat and employs a dual polarity power source, therefore safety precautions must be taken because of the high voltages.