Simple Stereo Headphone Amplifier Circuit using IC LM4910

LM4910 IC is special chip, it makes stereo headphone sound good by using a very low power, also the circuit is useful for small devices like MP3, phone, battery gadgets.

Furthermore, it work on low voltage to around 3.3V and has shutdown mode to save power.

This article for Simple Stereo Headphone Amplifier Circuit using IC LM4910 shows how to design, build and understand stereo amp with IC LM4910.

Circuit Working:

Parts List:

Components	Values	Quantity
Resistors	20k 1/4 watt	4
Capacitors	PPC 0.39µF	2
	Electrolytic1µF	1
Semiconductors	IC LM4910	1
	Stereo Headphone	1

Here, the circuit uses 3.3V DC power.

Audio come from left and right input and goes through capacitors C1 and C2 into LM4910 chip, then C1 and C2 blocks DC and only lets AC audio signal pass to amp.

After that, gain sets by resistors R1, R2, R3, R4 which are all 20k and give a balanced gain.

Then LM4910 boost signal and send to left and right headphone out and audio is clear and with low distortion.

Now capacitor C3 connects to pin 5 bypass, reduces power noise and keep output clean and finally, pin 3 is shutdown pin which connects to ground to turn OFF the amp and save power.

Formulas with Calculations:

Here are formulas and calculations for Simple Stereo Headphone Amplifier Circuit:

Formula for Gain:

Gain = R3 / R1 = R4 / R2

All resistors are 20k so:

Gain = 20k / 20k = 1 (unity gain)

Cutoff Frequency:

Formula:

fc = 1 / (2 × π × Rin × Cin)

where:

Rin is 20k
Cin is 0.39μF

fc = 1 / (2 × 3.14 × 20000 × 0.39×10⁻⁶)

fc = 20.4 Hz

So the circuit blocks signals below 20.4 Hz.

How to Build:

To build a Simple Stereo Headphone Amplifier Circuit using IC LM4910 follow below steps for assembling and connections:

• First, collect all parts from circuit diagram.
• Next, connect left audio input to pin 1 of LM4910 through capacitor C1.
• Then put resistor R1 between pin 1 and pin 8.
• Now connect right audio input to pin 2 through capacitor C2.
• Place resistor R2 between pin 2 and pin 7.
• So use switch or jumper at pin 3 for shutdown and to turn OFF the amp and connect pin 3 to ground.
• After that, connect pin 4 to GND.
• Further, connect capacitor C3 from pin 5 to GND which reduces noise and keep output stable.
• Connect left headphone output to pin 6 and put resistor R3 between pin 8 and pin 1.
• Next, connect right headphone output to pin 7 and then place resistor R4 between pin 2 and pin 7.
• Finally, give 3.3V power to pin 5.

Conclusion:

Overall, this project for Simple Stereo Headphone Amplifier Circuit using IC LM4910 is small, easy and works well; also it uses low power, need few parts and give clear sound.

Moreover, its good for hobby and for professional audio work and we can change design for different sound as per our needs.