Can single TDA7293 handle 100W RMS with 4 ohms?

[MMarg.1]

Hello,

I am planning to build amplifier based on single TDA7293 SoC, in class G (as described in technical note). I have 2 voltages, +22/-22 and +45/-45V. The speaker has 4 ohms. Can TDA7293 handle the 100W RMS power, or it is too much for single chip and I should use bridge model (two TDA7293 connected master-slave)?

When bridged, may I use same supply voltage?

The frequency is limited to range 10Hz- 150Hz.

best regards

M.

[Peter BENSCH · Accepted solution]

Welcome, @MMarg.1​, to the community!

This is a similar question that has been discussed in various forums for many years.

Theoretically, you can achieve an output power of approx. 145W with a TDA7293, +-45V and 4 ohms - however, as the data sheet in section 4.2 states, this is thermally unmanageable. With the circuit shown in Figure 8, you could save a little power dissipation, but the achievable output power still depends very much on the thermal resistance of the heat sinks, which you can only verify in appropriate test setups. Therefore, it cannot be promised that you will achieve your desired continuous output power of 100W without self-activating the thermal shutdown.

It is definitely not possible to operate the TDA7293 with your 4 ohms speaker in bridge mode, which is also stated in the data sheet, section 4.3. The main reason is the higher current, which is no longer manageable and would lead to overload:

Bridge application

Another application suggestion is the bridge configuration, where two TDA7293 are used.

In this application, the value of the load must not be lower than 8 Ω for dissipation and current capability reasons. [...]

Does it answer your questions?

Regards

/Peter

[MMarg.1]

Hi Peter,

thanks for answer. That's answer on my question. Do you have any other proposal I can achieve 100W RMS with any chip from ST? Shall I look into class D ?

best regards

M.

[Peter BENSCH]

With a Class-AB, 100W into 8 ohms is doable, but into 4 ohms it's a challenge, so it would be easier to go for Class-D.

One challenge with Class-D, however, is the interference radiation of the high-frequency Class-D signal.

Good luck!

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

[Piranha]

In the old times there where these:

https://www.eleccircuit.com/100-150w-super-hybrid-low-thd-power-amplifiers-using-stk-4048/

If you need one or few pieces, you can probably still get some of these. Otherwise you will have to make a circuit with some powerful discrete transistors. And in both cases you will need a pretty capable heat dissipation system.

> Do you have any other proposal I can achieve 100W RMS... Shall I look into class D ?

Yes. Especially for a dedicated sub-woofer amplifier it's almost a no-brainer.