Achieving excellent sound reproduction while preserving efficiency and dependability is crucial in the field of audio amplification.
This circuit for a 50 watt audio amplifier is an example of a well thought out way to provide powerful audio performance.
This amplifier circuit uses a combination of MOSFETs and BJTs to deliver a high fidelity audio experience, with the capacity to drive an 8 ohm speaker with a forceful 50 watts.
Circuit Working:
Parts List:
| Component Type | Specification | Quantity |
|---|---|---|
| Resistors | 15k | 1 |
| 1.2k | 1 | |
| 680Ω | 1 | |
| 560Ω | 1 | |
| 820Ω | 1 | |
| 10k | 1 | |
| 2.2k | 1 | |
| 10Ω 2W | 1 | |
| 47k | 2 | |
| 2.7k | 2 | |
| 4.7k | 2 | |
| Preset 1k | 1 | |
| Capacitors | Ceramic 220pF | 1 |
| Ceramic 68nF | 1 | |
| Electrolytic 47μF 50V (C2) | 1 | |
| Electrolytic 47μF 25V | 1 | |
| Electrolytic 100μF 50V (C6) | 1 | |
| Electrolytic 100μF 25V | 2 | |
| Semiconductors | MOSFET IRF530 | 1 |
| MOSFET IRF9530 | 1 | |
| Transistor BC556 | 2 | |
| Transistor BC546 | 2 | |
| Diode 1N4002 | 1 | |
| Inductor | Coil (12 turns of enamelled copper wire on a 1cm diameter plastic former) | 1 |
| Speaker | 8Ω | 1 |
The goal of this 50 watt audio amplifier circuit is to provide a high power output with the least amount of distortion.
Transistors Q1 and Q2 are used in a differential amplifier that powers the amplifier initially.
R1 controls the input current, capacitor C1 filters out undesirable high frequencies, and capacitor C1 functions as an input DC decoupler.
The driver stage which uses transistors Q3 and Q4, is the following step.
The MOSFETs IRF530 and IRF9530 are used in a complimentary push pull arrangement for the output stage.
The inductor L1 connects the output to the speaker.
Noise is reduced by the network using R14 and C5, and the power supply is filtered by capacitors C6 and C7.
The quiescent current is adjusted by preset VR1.
Put the circuit together using a +/-35V DC dual supply on a premium PCB.
On a plastic former with a diameter of 1 cm, wind 12 rounds of enameled copper wire for L1.
Other electrolytic capacitors can have a rating of 10 or 15V, but capacitors C6 and C7 should be rated at 50V.
The MOSFETs need a heat sink, bigger heat sinks are better.
An 8 by 4 by 4 inch finned aluminum heat sink will work.
Formulas:
Below are the relevant formulas for 50 Watts Audio Amplifier Circuit:
Stage of Differential Amplifier:
Q1 and Q2 transistors.
Capacitor C1 serves as a DC decoupler for input.
The intended cutoff frequency and the input sources impedance should be taken into consideration while choosing this capacitor.
fc = 1 / 2πRinC1
where,
- Rin is the input resistance.
- C1 is the decoupler capacitor for input in the circuit diagram
Output Stage:
MOSFETs: complementary push pull design using IRF530 N-channel and IRF9530 P-channel.
Coupling of Output: Using Inductor L1, the output is connected to the speaker.
The cutoff frequency may be used to calculate the value of L1 for an inductor intended to filter out high frequency noise.
L1 = 1 / 2πfcutoffCspeaker
where,
- Cspeaker is the capacitive load of the speaker system, typically minimal.
Network for Noise Reduction:
Together, resistor R14 and capacitor C5 create a network that attenuates noise.
The following provides the noise reduction cutoff frequency:
fnoise = 1 / 2πR14C5
L1 inductor:
On a plastic former with a diameter of 1 cm, wind 12 rounds of enameled copper wire, the formula for calculating the same:
L = lμ0 * μr * N2 * A / l
where,
- The permeability of empty space is represented by μ0, the relative permeability by 𝜇𝑟 , the number of turns by N, the cross sectional area by 𝐴A, and the coils length by l.
How to Build:
To build a 50 Watts Audio Amplifier Circuit follow the below mentioned steps:
- Gather all the components required in the above circuit diagram.
- Connect collector of Q1 transistor to negative supply of -35V through resistor R12, and between collector Q1 and resistor R12 connect to resistor R11 to base of transistor Q4, connect base of transistor Q1 to audio input and to ground through resistor R1, connect emitter transistor Q1 to emitter of transistor Q2, and connect resistor R2 and capacitor C1 from base of transistor Q1 and ground.
- Connect collector of transistor Q2 to negative supply pf -35V, base of Q2 to ground through resistor R13 and capacitor C4, and connect emitter of Q2 tp emitter of Q1, between base of Q2 and resistor R13 connect resistor R5, capacitor C3, and resistor R10 to positive supply.
- Connect collector of transistor Q3 to resistor R9 as shown in circuit diagram, connect base of Q3 to center leg of preset VR1, and emitter second leg of VR1 through resistor R6.
- Connect collector of transistor Q4 to emitter of transistor Q3, base of Q4 to collector of Q1, and emitter of Q4 to negative supply of -35V.
- Connect MOSFET Q5 gate to emitter of transistor Q3, drain of Q5 to negative supply of -35V, and connect source of Q5 to source of Q6 MOSFET, connect source of Q5 to one end of inductor L1 and other end to one end of 8 ohms speaker and other end of speaker to ground.
- Connect resistor R14 and capacitor C5 from source of Q5 MOSFET to ground, and connect positive of capacitor C7 from negative of -35V to ground.
- Connect MOSFET Q6 gate to positive supply through diode D1, and between this connect a resistor R8 and resistor R7 to third leg of preset VR1, connect drain of MOSFET Q6 to positive supply of +35V, and connect source of Q6 to source of Q5.
- Connect capacitors C2 and C6 as a filter capacitors to clean the ripples.
Conclusion:
This 50 watts amplifier circuit uses a careful component arrangement to provide a loud and clear audio output, providing a reliable solution for audio amplification demands.
This circuit is meant to deliver consistent and excellent audio performance, whether it is utilized in a professional setup or a home audio system.