Saturday, January 24, 2015

Headphone Amplifier With TDA2822

Welcome back everyone, its been a long time since I was thinking about writing a headphone amplifier which is simple to built but has good functionality. So here it goes, a headphone amplifier that can be used in anywhere.

Sometimes we come across high impedance headphones like 600ohm or so. If anyone drive them with the built in sound card of a computer motherboard or try to run it from any other similar device he might not get that expected volume level. This amplifier could be a cheap solution for that problem. Also it can be a great project too.

In the very heart of this design we have the integrated circuit called the TDA2822. This chip is a low voltage power amplifier that comes in a small 8 lead Minidip package and got some excellent features such as

1. Supply voltage ranging from 1.8V to 15V, so very versatile and can be used in anywhere.
2. Low crossover distortion.
3. Low quiescent current (max 9mA), so you can keep it running without load for very long time.
4. Can be used both in Bridge tied load and stereo configuration.
5. Small packaging makes it ideal for compact designing.

Now lets take a look at the integrated circuit's pin configuration

Pin configuration of TDA2822

From the pin configuration it is pretty obvious that its diagram will be really simple. So let's dive in the stereo diagram first.

Stereo Configuration

The diagram is straightforward and simple. We have two inputs from a stereo audio jack, could be from anywhere from computer or mp3 player or any similar thing.

Input 100kohm variable resistors can be gang type and is used for controlling the volume.

You can add a input decoupling capacitor if you want. Could be 4.7uF or 10uF.

If the power supply does not come with its smoothing capacitor, you might need to add one with the supply voltage pin. Again could be anything from 10uF to 220uF or so.

Output decoupling capacitor can have less capacitance, circuit will still work but you may loose some bass response. Do not skip the 0.1uF non polar capacitor and the 4.7ohm resistor, these are used for the stability of the diagram.

Now if you need more power per channel, you can use this chip to design a bridge amplifier. Here is the diagram. 

Bridge Tied Load Configuration

As you can only the one input of this chip is used this time and the other is grounded, you can swap pins and the 10uF and 0.01uF capacitor with the pin 5 and pin 8, diagram should work just fine.

Again here nothing much to be said, you can add input decoupling capacitor here too, but no need of output capacitor this time.

Bridge mode will be significantly more powerful than the stereo. In stereo configuration you will get 300mW on a 32ohm load with 9V supply where in Bridge you will get 1000mW in similar condition. Worth mentioning with 10% distortion. 

Power supply for this.

As I was saying voltage supplied for this diagram can vary from 1.8V to 15V but lower the voltage will be, lower the output power will be. 

This circuit can be powered from almost anything, you can use an USB cable or single lithium ion cell to provide power, if you intend to use with low impedance headphones.

You can use another power supply using regulator chips like 7809 or 7812 if you want to use high impedance headphones or maybe you can use two or three lithium ion batteries in series.

Make sure not to let any noise from power supply enter the circuit. You can use this diagram too.

Power Supply For the diagram

Here 0.1uF capacitor is used for cancelling the noise from power supply. A simple transformer and a bridge rectifier can be used with this. Make sure to use proper grounding of the whole circuit to lower the noise.

So hope you enjoyed reading this post and hope you might give it a shot too. Happy experimenting!

Datasheet for TDA2822.
More about linear voltage regulation.
Using USB port power for powering other devices.
Index of my other posts.