Big bulky speakers are a thing of the past for sound systems.
Today most systems use a special part called a complementary output stage to make them smaller and work better.
This article will take a look inside a small 1 watt amp and show how it works step by step.
What is a 1 Watt Hi-Fi Amplifier Circuit:
A 1 watt Hi-Fi amplifier circuit is an electrical circuit designed to improve high-quality Hi-Fi audio signals.
It has a power output of around 1 watt.
The ability to generate audio signals with low sound and excellent clarity is what defines hi-fi amplifiers.
This amplifiers 1 watt power output is frequently seen in compact audio systems, desktop speakers and headphone amplifiers.
Circuit Working:
Parts List:
| Component | Value | Quantity |
|---|---|---|
| Resistors all resistors are 1/4 watt | ||
| 68Ω | 1 | |
| 1M | 1 | |
| 1Ω | 2 | |
| 1k | 1 | |
| Potentiometer | 5k | 1 |
| Capacitors | ||
| Electrolytic | 4.7µF, 250µF,100µF | 1 each |
| Semiconductors | ||
| Transistors | 2N3904, 2N2430, 2N2706 | 1 each |
| Speaker | 4Ω | 1 |
| Battery / DC Supply | 9V | 1 |
Similar output stages with NPN and PNP power transistors are found in the 1 watt Hi-Fi amplifier circuit that forms the basis for modern sound systems.
The steps involved in circuit operation are described below:
When the input signal reaches the circuit it comes into contact with the volume control RV1 which acts as a volume knob to adjust the signals strength.
The first stage amplifier the Q1 transistor receives the modified signal from the volume control.
The speakers and resistors R1 and R5 make up its collector load.
The voltage at the collector is around 4.5V which is half of the supply voltage.
When the voltage at 4.5V matches the collector voltage the emitters of Q2 and Q3 merge at that junction.
The current passing through Q2 and Q3 is limited by low value resistors R3 and R4.
Q2 stays active and Q3 stays OFF while the input signal that Q1 amplified stays below 4.5V or roughly half the supply voltage.
Q2 switches OFF and Q3 takes over when the signal voltage exceeds 4.5V.
After merging at their shared emitter junction the amplified signals from Q2 and Q3 pass through electrolytic capacitor C2 which is connected to the loudspeaker.
To keep things stable and reduce distortion negative feedback is essential.
Resistors R5 and R2 which slightly reduce the circuits gain make this possible.
Although thermistors or diodes are frequently used in current designs to avoid overheating and protect the output transistors and the resistor R1 supplies base bias for Q2 and Q3.
Output:
This challenging circuit produces a remarkable 1 watt output with little noise which enhances the hi-fi systems excellent sound quality.
Formulas:
One can create a 1 Watt Hi-Fi amplifier circuit by including a simple transistor amplifier circuit using all of the circuits parts mentioned above in the circuit diagram.
The general formula for the circuit diagram is as follows:
Calculating Power:
The power supplied to speaker P can be estimated using the formula below:
P = Vpeak2Rload
where,
- Peak voltage swing is referred to as Vpeak.
- Rload for the 4 ohm speaker impedance
By following this simple method users can construct a 1 Watt Hi-Fi Amplifier Circuit using the transistors and other circuit parts that are shown in this article.
Adjustments are required based on specific requirements, component availability and desired circuit performance features.
Advantages and Disadvantages:
Advantages
- Modern sound system designs when space is limited might benefit from the additional output stages space efficient solution.
- The circuit produces a 1 watt output with very little noise assuring an output of high quality sound.
- The circuits stability is enhanced by biasing and negative feedback which protect against damage to the output transistors.
Drawbacks
- Because the circuit has DC coupling a single transistor modification can have a big effect on the circuit as a whole.
- To reduce this problem it is recommended to use matched pairs of transistors for the output stage.
How to Build:
Below mentioned are the connection steps for building the 1 watt Hi-Fi amplifier circuit:
- For the most accuracy begin by choosing matched pairs of NPN and PNP power transistors for the parallel output stage.
- To change the signal strength connect the input signal to the volume control RV1.
- Connect the signal through C1 to protect it from unwanted DC components.
- Connect the modified signal to the first stage amplifiers Q1 transistors base.
- To start the output stage connect the loudspeaker and Q1 collector load using resistors R1 and R5.
- To control the current flowing through Q2 and Q3 use resistors R3 and R4.
- Based on the signals strength in terms of 4.5V allow signal switching between Q2 and Q3.
- Resistors R5 and R2 are used to ensure negative feedback which fixes the circuit and lowers noise.
- For base biasing of Q2 and Q3 use resistor R1 or think about adding thermistors or diodes for thermal protection.
- Also yes finish the circuit by using electrolytic capacitor C2 to connect the amplified signal to the speakers.
Conclusion:
This carefully designed 1 watt Hi-Fi amplifier circuit has become an essential part in modern sound systems.
Circuit designers choose it because of its stability, minimal distortion and compact size.
Everyone are welcome to play around with this circuit and improve the circuit design skills.
Please feel free to ask for help or if there are any queries.