Bridge tied 5V audio amplifier using LM4876 IC.
This Simple 5V Audio Amplifier Circuit using IC LM4876 make sound louder and is good for small speaker in portable device.
Hard to make small amplifier with low power need.
LM4876 chip give 1 watt output and is good for this job.
It turn ON/OFF with simple logic and uses very low power which is great for portable and low voltage use.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | 20k | 3 |
| Capacitors | PPC 0.39μF 100V | 1 |
| Ceramic 0.1μF | 1 | |
| Electrolytic 1μF 25V | 1 | |
| Semiconductors | IC LM4876 | 1 |
| 8Ω speaker | 1 | |
| ON/OFF switch | 1 |
The circuit is small and LM4876 need only few extra parts which come in 8-pin small box.
Audio goes into pin 4 (-IN) through resistor R1 and capacitor C1.
Resistor R2 control gain with feedback.
Switch with resistor R3 connect to shutdown pin to turn chip ON/OFF.
Pin 5 (VO1) and pin 8 (VO2) goes to 8 ohm speaker.
Chip work in bridge mode and uses two amps with 180° phase shift to give more power to speaker.
Formulas:
Important things to know when making 5V audio amp with LM4876:
Gain Formula if using resistors:
LM4876 can work with or without R1 and R2.
If using them then gain:
(Av) = R2 / R1
where,
- R1 connect input pin to audio signal
- R2 connect input pin to ground
Power Dissipation (Pdiss):
Check chip does not overheat.
Formula: Pdiss = (Vcc − Vout) × Iout
where,
- Vcc is power supply with max 5.5V
- Vout is output voltage which is near of Vcc
- Iout is current to speaker
Efficiency (η):
η = (Output Power / Total Power) × 100%
Depends on speaker load and supply voltage
Note:
With these formulas we can build and check our 5V amp using LM4876.
See LM4876 IC datasheet for more details.
How to Build:
To build a Simple 5V Audio Amplifier Circuit using IC LM4876 follow the below mentioned steps:
- Collect all parts as shown in circuit diagram
- Pin 1 of IC1 connects to ground through ON/OFF switch.
- Pin 2 connects to pin 3 of IC1.
- Pin 3 connect to + side of C2 and other side of C2 to ground.
- Pin 4 connects to audio input through R1 and C1.
- R2 connects between pin 1 and pin 5.
- Speaker connects across pin 5 and pin 8.
- Pin 6 connects to +5.5V supply.
- Pin 7 connects to ground.
- Pin 8 connects to one end of speaker.
- R3 connects to +5.5V supply via pin 1.
- C3 connect from +5.5V supply to ground.
Safety Tip:
- IC LM4876 can get hot at 5V use.
- Use heat sink on chip to remove heat.
- Heat sink is the metal part that cools chip.
Conclusion:
This Simple 5V Audio Amplifier Circuit using IC LM4876 is small, low power and is good for portable devices.
But watch for heating when running at 5V as chip needs cooling.