Audio poweramp TDA2003

[HellasTechn]

Good day dear friends.

Once again i hould like to express my gratefulness for this lovely site.

Today i am working on on building an audio power amplifier.

I have chosen the TDA 2003 for this purpose because of it's low cost and the power output of 10W that it promises (that is all the power i will need).

Here is the circuit i found online :

There was a comment mentioning that i should add proper ground decoupling. What exactly is ground decoupling ?

dont capacitors C1, C2 act as decoupling capacitors ?

Thank you very much !

 

[KrisBlueNZ]

Based on prior experience I wouldn't trust any design from circuitstoday.com, but in this case this one is copied directly from the manufacturer's data sheet:



Yes, the 100 µF and 100 nF capacitors at the top are decoupling capacitors. The 100 nF one should be a ceramic capacitor and should be connected as closely and directly as possible between pins 5 and 3 of the TDA2003.

I've not heard of "ground decoupling"; I can only assume it refers to the +V_S rail being decoupled to the 0V rail. Perhaps it has some other meaning.

The angled faint print on that diagram says "Obsolete Product(s)" and you should heed that warning. The IC could become unavailable at any moment.

Here are some alternatives you could look into:

http://www.digikey.com/product-sear...326,79c032e&ColumnSort=487&stock=1&quantity=1

 

[HellasTechn]

No worries about that . i already bought the TDA2003...

Strange... what could it mean???

here is exactly what they say :

• ground must be properly decoupled.
• Speaker K1 can be a 4 ohm one.
• TDA2003 must be fitted with a heat sin

 

[HellasTechn]

I found a few other designs also. probably better.

Picture 1 and picture 2 are the same...


You know what i should have got the TDA2005 or TDA2030. I only chose the 2003 because i have a serius limitation. i only have a transformer 115v to 12v 1 Amp...

 

[KrisBlueNZ]

here is exactly what they say :

• ground must be properly decoupled.
• Speaker K1 can be a 4 ohm one.
• TDA2003 must be fitted with a heat sin

Is that text on circuitstoday.com? If so, I'd just ignore it. But you will need a heatsin (actually, a heatsink might be better).

I would stick with the design that the manufacturer recommends.

 

[HellasTechn]

Yes i will use a Heatsink and a quite large one (i only have one size lol) and i think i will go with the recommended diagram.It wouldn't hort to play a little and see though.

My concern is will it require more than 1 amp from my transformer ? i guess that if i use 12V it will not but power output will also be lower.

yes this text was on circuitstoday.com
here is the URL : http://www.circuitstoday.com/10w-amplifier-using-tda2003

 

[KrisBlueNZ]

Ignore anything you read on circuitstoday. If you haven't already, download and read the manufacturer's data sheet: http://www.st.com/web/en/resource/technical/document/datasheet/DM00028077.pdf.
With a 12V DC supply into a 4 ohm load, the maximum output power is only 4W. Into an 8 ohm load it will be only slightly more than 2W. With a 4 ohm load at 4W continuous, the peak output voltage is sqrt(32) and the peak output current is sqrt(2) or 1.414A. As long as you have a big decoupling capacitor (at least as much capacitance as the output coupling capacitor), a power supply that's rated for 1A will be OK.

If you want higher output power with a limited supply voltage, your first option is to use a bridge-tied load (BTL) amplifier - many of the ones on that Digikey page can be used in that configuration - and your second option is to use a lower load (speaker) impedance.

 

[HellasTechn]

So useing the materials that i already have my only option is to try useing a higher voltage transformer.
The problem is that here in Greece we only use 220volts and i cant find 115volts transformer. The bad thing is that for the project i am working on 100v transformer is a MUST.

So what if i modify the diagram and use +- 12volts ? i think i have a +- 12v power supply.

 

[davenn]

So what if i modify the diagram and use +- 12volts ? i think i have a +- 12v power supply.

Do you have a suitable transformer with a centre tapped secondary to make a split rail PSU ?

Dave

 

[HellasTechn]

I do have one that it is rated 2x10v 0.7 amps. But to be honest i dont know how to make a split rail psu.

ps. i gave it a look and i think i can make it. let me post a schematic.

 

[KrisBlueNZ]

You can't use a ±12V or ±10V power supply. Check out the maximum supply voltage for the TDA2003A. This is from the data sheet.



You should be able to find a switching power supply that can run from 100 VAC and produce 18V at 2~3A. A switching supply is not the simple kind of power supply that runs the transformer at 50 Hz then rectifies and smooths the secondary; it uses a smaller, lighter transformer that is driven at high frequency by a switching circuit. These are available in a wide variety of output power levels, output voltages (including adjustable output voltages), and input voltage ranges; many of them have "universal" inputs, meaning they can operate from 100~250 VDC with no change, or only a moderate change, in the available output power.

Failing that, I would suggest using a BTL amplifier.

 

[HellasTechn]

Now that is what i call discouragement.... Since i have no other materials in my hands i will try the split rail psu and if that cant do the job then i will try a switching psu. (the transformer i have connected as aplit rail psu will be able to provide about 1.4amps right ?

I want to dig into the switching psu's anyway.

ps. There are so many things that i want to ask that i dont know where to start from...

Later this month when i get to have some free time i would like to ask you about switching PSU's that use optocouplers.
I really cant understand how you can switch on and off such a power supply (and not only that)...

 

[Arouse1973]

As Kris mentioned here it is in bridge mode.



Thanks Adam

 

[KrisBlueNZ]

Since i have no other materials in my hands i will try the split rail psu and if that cant do the job then i will try a switching psu. (the transformer i have connected as aplit rail psu will be able to provide about 1.4amps right?

It's rated for 2x 10V AC at 0.7A? Put the two secondaries in parallel (make sure they're in phase) and feed them through a 3A bridge rectifier into at least 4700 µF of smoothing. You'll get around 12~15V DC under slight load, dropping a few volts under heavy load. With a single TDA2003A you'll get about 3W into 4 ohms, or about 2W into 8 ohms.

I want to dig into the switching psu's anyway.
ps. There are so many things that i want to ask that i dont know where to start from...

A Google search is an excellent place to start. There's a lot of tutorial and explanatory material around on the web. When you find stuff that's relevant, Google again using the keywords that you find in that material, to find more relevant stuff.

Later this month when i get to have some free time i would like to ask you about switching PSU's that use optocouplers. I really cant understand how you can switch on and off such a power supply (and not only that)...

Google will find articles that explain switching power supplies. Always the best place to start.

As Kris mentioned here it is in bridge mode.

Nice. Thanks for that Adam. I think he may only have one TDA2003, unfortunately.

 

[Arouse1973]

Ok no probs.

 

[HellasTechn]

Yes i only have one... (last one at the shop)

Ok here are the test resaults...

For an input voltage range of 6 to 20 volts the amplifier works and useing my portable mp3 player as input it draws 1/4 Amps
useing two speakers 8 ohms in paralel (4 ohms total) and 3w each. I noticed no change in current through this voltage range. The 2003 started drawing more miliamps as i raised the input signal volume and also started getting a little hot (I did the test without heatsink).

So i think that with 12-18V 2 amps transformer i will be ok but i might need to use a preamplifier to get more power.

 

[Arouse1973]

Sounds good to me ha ha. Nice one
Adam

 

[BobK]

You don't need a preamp. You can change the gain by changing R2. It is set for 10 now. Halve it and you will get a gain of 20. But notice the effect on Rx Cx to maintain the same frequency response.

Edit: Actually the gain should be 100 now. That should be more than enough to drive the amp into distortion from an MP3 player output.

Bob

 

[HellasTechn]

I will play with the resistors ant the capacitor and i am confident i will get better resaults. THANK YOU All

 

[HellasTechn]

I hve got a trimmer of 100 Ohm. That sould allow me to play with gain. now about frequency ragne i only need
800Hz to 8Khz.