# Does this circuit work?

Discussion in 'General Electronics Chat' started by MWG, Dec 24, 2009.

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1. ### MWG Thread Starter Member

Apr 15, 2009
28
0
I'm trying to make a small audio amplifier based on the TDA2030.

I was planning on building the circuit shown in the datasheet but then i found the one below which is more suitable as i only have 10w speakers

http://www.zen22142.zen.co.uk/Circuits/Audio/tda8.htm

I modelled up the circuit in multisim and sent a 1Khz sine wave into it but the output is a constant 1.4V

I can't see why it wouldn't work but then i'm still learning about this stuff, if i built this circuit would is work or not?

2. ### SgtWookie Expert

Jul 17, 2007
22,183
1,732
Don't know why, but the image of your simulation didn't attach.
.png format images are preferred, as they are not "lossy" like .jpg images are.

What is the amplitude of your 1kHz signal?

Did you run the simulation for at least 10mS, and use a max step of around 10uS?

3. ### t06afre AAC Fanatic!

May 11, 2009
5,939
1,222
I think you should download the TDA2030 data sheet. In this document you will find many recommended circuits diagrams. This is your thread so post again if you have more questions rearding your project

4. ### MWG Thread Starter Member

Apr 15, 2009
28
0
Hey Sgt

I didn't attach a copy of my simulation, here it is

the signal is 200mV p-p so should be big enough, i took the scope down ton 10ns and its till a flat line so obviously something is wrong.

Edit: as far as i can tell the test circuit in the datasheet is the same but with different values for R1,R3 and R4

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5. ### bertus Administrator

Apr 5, 2008
15,938
2,439
Hello,

There is no load in your simulation.
Put a resistor of 8 Ohms at the output as load.

Greetings,
Bertus

6. ### SgtWookie Expert

Jul 17, 2007
22,183
1,732
OK, what's happening is that in the circuit you linked to, they are using a double-rail supply (ie: +15v and -15v).
You are using a single-rail supply of 12v.

You'll need to add another 47k resistor at the junction of R4/C3/U1 pin 1 going to Vcc to bias the input at Vcc/2.

You will also need a large cap (1,000uF-2,200uF) between the junction of R2/U1 pin 4 (output) and the speaker to block DC from flowing through the speaker.

If you're planning on using this in an automotive environment, you should increase Vcc to 14v.
[eta]
You'll need to use an 8 Ohm resistor from the other side of the output cap to ground to simulate the speaker load, or Multisim will complain about floating nodes when you attempt to simulate it.

Last edited: Dec 24, 2009
7. ### S_lannan Active Member

Jun 20, 2007
247
2
does the tda2030 in multisim actually have a spice model?

8. ### MWG Thread Starter Member

Apr 15, 2009
28
0
Once again Sgt you've sorted me out

One thing though, the sine wave doesn't look much like a sine wave . It looks more like a square wave, could that be clipping?

9. ### SgtWookie Expert

Jul 17, 2007
22,183
1,732
If you've used too small a DC blocking cap or omitted the 8 Ohm load, you'll see very bad clipping.

10. ### MWG Thread Starter Member

Apr 15, 2009
28
0
I've put in a 2200μF cap between pin 4 and R2, its almost the perfect square wave still? could the gain be set too high?

11. ### dsp_redux Active Member

Apr 11, 2009
182
5
What's the tension mesured on your square wave?

12. ### MWG Thread Starter Member

Apr 15, 2009
28
0
i'm not sure what you mean by tension but it goes between 5V and -5V and has a period of 1ms if that helps?

13. ### dsp_redux Active Member

Apr 11, 2009
182
5
The TDA2030 needs at least 12V on single-rail supply, +-6V dual-rail. If the biasing is correct, you should be able to approach to upper and lower value you give to your op-amp. +-5V is definitely not supposed to clip on a dual railed +-12V supply. Have you used the single-rail supply like SgtWookie proposed you? Can you post the mods you have done to your circuit?

14. ### MWG Thread Starter Member

Apr 15, 2009
28
0
I was playing with the values of R1 and R3 earlier and must have gotten confused as they were not even close to what they should have been, i've put them back to what they were and its definitely a sine wave now

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15. ### Audioguru New Member

Dec 20, 2007
9,411
896
With a supply that is only 12V the TDA2030 barely works because that is its minimum supply voltage.
Its output power might be only 1W or less.

The input must me no more than 78mV RMS or 0.11V peak.

Now you have R3 and R4 swapped backwards. The gain is slightly more than 1 and the TDA2030 will probably oscillate at a high frequency.

16. ### MWG Thread Starter Member

Apr 15, 2009
28
0
i know the power is on the lower end of what it can be, i haven't decided on what i'm going to use for a power supply as of yet.

i guess you aren't called audioguru for nothing, i swapped the values of R1 and R3 and it was still a square wave, dropped the input to 50mv p-p and its working as it should now

17. ### dsp_redux Active Member

Apr 11, 2009
182
5
I don't see why you say R3 and R4 are swapped Audioguru? R4 = R6 so you have Vcc/2 on the non-inverting input.
\begin{align}
V^+ &= V_{in}\\
V^+ &= V^-\\
\frac{V_{out} - V^-}{R_3} &= \frac{V^- - 0}{R_1}\\
V_{out} &= R_3 \frac{V_{in}}{R_1}+V_{in}
\end{align}

So the gain depends on R3 and R1. Or I made a mistake? Or I misread?

Last edited: Dec 24, 2009
18. ### SgtWookie Expert

Jul 17, 2007
22,183
1,732
If you're going to use such a low voltage for a supply, you really need to use a push-pull type "bridge" amplifier.

19. ### Audioguru New Member

Dec 20, 2007
9,411
896
Sorry I got the numbers mixed up.
You have 1.5k for R3. It should be and was 47k.
You have 47k for R1. It should be and was 1.5k.

Then the gain will be 32.3 times.

20. ### MWG Thread Starter Member

Apr 15, 2009
28
0
I was under the impression that it didn't matter which way round they went, however if they are ordered as they are in the last diagram i attached the output signal amplitude reduces dramatically so it seems to be right that they were reversed

Sgt,

The datasheet states in the main table that with 14V supply voltage it has an output power of 14W with 4Ω speakers or 9W with 8Ω.

I have 1x 4Ω 10W speaker and 1x 4Ω 5W speaker, if i hook them up in series they'll become and 8Ω RL, the amp supposedly will only have 8W output at 12V so shouldn't be enough to blow the speakers, right?

I'd like to add that i am just playing with this amplifier, i find making and doing a better way to learn than just reading about it