Max power out on small chip amps tested

[johnr66]

I wanted to see what the maximum power output before clipping is on a few chip amps are, so I set up a test. Using a regulated 9 volt supply, non inductive 4 and 8 Ohm load resistors and a 200Hz sine wave source, I set up a test.

To find the highest clean output before clipping, I used an oscilloscope on the output to monitor the waveform. I increased the input signal until clipping began and backed it off just to the point of no clipping then took the RMS voltage reading across the load resistor.

The results:

LM386: This chip's weak drive current inhibits its ability to drive 4 Ohms loads. 8 Ohm loads are okay, but far from the best.

TDA2050: Although this IC is designed for much higher supply voltages, it's internal bias turns on at a very low voltage and it works fine for a low voltage amplifier (tested at +4.5/-4.5v). It drives 4 Ohms loads higher than the LM386 but is far from the "Swing King". Because it is designed it operate at much higher Vs, there is no need to optimize it's output swing like the low voltage ICs need so I included it here mainly for interest.

TDA7231: This middle aged (1980's tech) IC has improved output swing into 8 Ohms and much improved into 4 Ohms as compared to the LM386.

TDA1517: This is a later generation chip requires minimum parts and delivers a high output swing without need for a bootstrap capacitor. (one channel driven)

TDA2003: This middle aged IC was designed for maximum output swing for automotive use. It is about the same as the TDA1517.

TDA7276A: This later generation IC delivers the highest voltage swing than any of the others. It is the "Swing King" so far.

Vs-1.2v: this is the supply voltage minus the Vsat voltage of the upper and lower output transistors. I used .6 volts per transistor. The chart shows the maximum rms sine wave power (clean power) possible under this condition. With 8Ohm loads, many chips were close or tied it, but at 4 Ohm loads, for whatever reason, the ICs fell short.

[superR]

Do you have the same measurements for 12 of 15 Volt DC supply? I think that is where the "men separate from the boys". At 9V, the resistors don't require much current to be driven. At 12V or 15V, delivering the current will be much higher/difficult.
Nice idea of testing though!

[johnr66]

I plan to test at other voltages (if the chips that will operate at these voltages). 4.5, 6, 12, 15 and The TDA2050, LM1875 at +/- 18, 20 and 22 volts. In the case of the last two chips, I'd have to come of with hefty regulated dual supply.

[Th3 uN1Qu3]

Any chance you can get the TDA2822M and TEA2025 tested too? They have been around for a long while and they are still extremely common. The 2822M is my favorite low-power chipamp.

[johnr66]

Originally Posted by Th3 uN1Qu3

Any chance you can get the TDA2822M and TEA2025 tested too? They have been around for a long while and they are still extremely common. The 2822M is my favorite low-power chipamp.

I happen to have both of these ICs and can test. I suspect the 2822M will be similar than the TDA7231A (mono) and 2824 (stereo) as they seem to be similar amplifier design in different packages with the 2822m derated due to the limited ability to dissipate waste heat.

[EBM_dude]

The TDA2822M makes a phantastic headphone amp. I'm interested as I plan on using it for that purpose. Too bad it can only tolerate 15V.

[Th3 uN1Qu3]

Originally Posted by johnr66

I happen to have both of these ICs and can test. I suspect the 2822M will be similar than the TDA7231A (mono) and 2824 (stereo) as they seem to be similar amplifier design in different packages with the 2822m derated due to the limited ability to dissipate waste heat.

Thanks. I'd appreciate it if you'd test it in bridged mode - it packs quite a punch, too bad it gets quite a bit of hiss due to the ridiculous amount of gain when bridged.