TDA2003 - 10W Car radio amplifier

The TDA2003 is a cheap amplifier that is designed to run on single rail power supplies. It has many applications (including in car systems if you do not need to show off down the high street with your subwoofers!) and is protected against short circuits in almost every way you would think them possible.

Here are some applications it would be happy to work as:

  • A pair can form a capable amp for a stereo system (i.e. a home made or upgraded midi system or 'ghetto-Blaster', although battery operation may not be possible).
  • This amplifier can be used to complete surround sound systems (i.e. centre and rear channel amps). I uses this amp for my centre channel in my old surround sound system.
  • A pair can be used to improve the sound from a NICAM TV, or even one may be used to improve a mono TV.
  • Beefing up those 400W+ amps in PC speakers (seriously)!
  • Tweeter or mid range amplifiers in bi-amp or tri-amp systems.

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This amplifier is based on the typical application in the ST Microelectronics datasheet. The performance from this circuit is very satisfactory. The sheet contains data for typical noise and distortion statistics, I cannot confirm these statistics because I don't have the equipment, but my ears tell me that the sound is good and with sensitive speakers, this amp will show some power.

The circuit is very simple as can be seen, however you will have problems with stripboard mounting due to its irritating pin layout. It is possible, but you will find this amp A LOT easier to build on a PCB. Unfortunately, the PCB layout suggestion in the datasheet is a copy of the bridge version suggested layout below it for some reason, so make sure you don't copy it and design your own.

If you must use stripboard however, this is how I would mount them. First straighten all the pins, then cut them to the length of the shortest two. Now you need to spread them out so they will fit into the stripboard. Do not spread them too much or they will break and your TDA2003 chip becomes useless.

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Resistor are recommended as 1% metal film, but as the picture of my prototype shows below, 5% resistors are capable (the cream coloured ones), except for the critical Rx resistor, which should be 1%. R2 and R3 are low value resistors and (unlike me) you should try and get close tolerance resistors for these. Capacitors should be electrolytic above 1uF and rated at 25V minimum. They must all be connected the right way round or failure and possibly injury will follow when the amp is powered up.

Rx and Cx must be worked out using the data sheets mathematical calculations. If in doubt however, I used 39 ohm for Rx and 33nF for Cx. Other non-electrolytic capacitors can be any type available. I used polyester layer capacitors because they have a closer tolerance (i.e. 5%) than most other capacitors.

A heatsink is important. The one shown in my prototype is actually too small and you should obtain something bigger for improved operation (unless your working with small voltages).

Power Supply

Before wiring a power supply, take note of this:

THE POWER SUPPLY REQUIRES MAINS VOLTAGE WIRING. DO NOT WIRE IT UNLESS YOU ARE SUITABLE QUALIFIED, DEATH OR SERIOUS INJURY MAY RESULT.

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If in doubt, do not wire your own transformer and get a pre-built one. The power supply is simple to wire and my prototype board already has it wired in. You cannot see the bridge rectifier because it is hidden behind the huge 4700uF 35V capacitor. You can see that I added an LED though, this is easy to do and needs 1.2k resistor, 5% tolerance is fine.

I cannot remember what transformer I used when I powered this amp, but do not use anything that gives more than DC 18V. This means that the transformer should be no more than 12V ideally.

You could get away with a small transformer such as around 30VA with 2-wire AC outputs.

Bridge Versions

There are two bridge versions available in the ST data sheet. A 20W version is below and performance from this circuit should be good.

The circuit is more complex, but should not pose any great layouts. Again PCB's are recommended as there are now two TDA2003 chips.

An alternative is the low cost bridge amplifier which has a small component count and an output power of 18W. All you need is several 0.1uF caps, plus a 1nF and a 10uF electrolytic. Put in one resistor, and there you have it. I must add though that a did try wiring this circuit on stripboard and the amp refused to work. You may have more luck than me but it would be more comforting if you used PCB instead, especially as the ST Microelectronics datasheet does contain a very nice looking layout for it as shown below:

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. Note: The above image is copied directly from the datasheet and is not mine, nor is it likely to be 1:1 scale. To achieve this scale, the best idea is to print to PDF file to A4 paper. Please use the datasheet to view the schematic and the component values.

As always, do not go for loads lower than 4 ohms (this includes two 8 ohm loads in parallel) and do not short the loudspeaker to ground.

Performance and Prototype Photo:

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My prototype works well. This board not only includes the amp, but its power supply and a very simple passive crossover (that's the axial electrolytic you can see bottom left). This allows a woofer and tweeter to be added with ease in the proposed system. You may notice the pins on the TDA2003 chip. They are spread out like they have to be when stripboard mounting. This is because this chip was used on my stripboard bridge version that failed. I also failed to remove the second chip without breaking the leads, so that headed for the bin.

Inputs are also on the left and the AC is the green and white wires appearing at the back. You can also see an LED at the front, this was to ensure me that everything in the supply was fine. The large 4700uF and 1000uF capacitors hide a few of the components.

The sound is quite impressive, with response across the audio spectrum. This amp will not go very loud though, turn it up and it will clip. I would expect better performance from the bridge versions, I am proposing to build one and will update this page with its performance. The bridge version (especially the low cost one) may actually beat the TDA2040 on price, but that depends on your supplier.