Recently I am building a circuit to drive loudspeaker and earphone.
The circuit was the same as the reference design (Fig. 1 of Page 4) of datasheet (http://www.kynix.com/uploadfiles/pdf9675/TDA2822.pdf).
It works fine with 8 ohm loudspeaker but makes earphone hot if I replace loudspeaker with small earphone.
Is the output power of TDA2822M too big for small earphones?
Is it possible to fix this situation by modifying the circuit?
Thanks for your help!
Loudspeaker is 8 ohms, earphone is how many ohms?
Quote from: digi2t on May 18, 2017, 06:41:15 AM
Loudspeaker is 8 ohms, earphone is how many ohms?
Probably 16 or 32 even. But I would imagine it's too much regardless.
hot at what sort of volume ??
I suspect you might have DC on the output or a high frequency oscillation.
Quote from: Rixen on May 18, 2017, 06:12:24 PM
hot at what sort of volume ??
I suspect you might have DC on the output or a high frequency oscillation.
This is along the lines I was thinking. The 0.1uF and 4.7 ohm to ground look like a gain/phase compensation network to me -- which is based on an expected 8 ohm load.
As a test, add an 8 ohm speaker in parallel with your headphones and see if they stop getting hot.
Another test is to stick an ammeter in series with the headphone and check for DC current. Maybe your capacitor is leaky or there is a wiring problem where you are somehow taking the output directly off the amplifier pin.
A nominal 1.7 watt @ 8-ohm amplifier operating from 5V sounds like it's fine for headphones as long as it is stable. Sure you can heat up your headphones if you're driving them too loud, but if you need to hear your music that loud you should get some headphones designed for that kind of power...or have your hearing checked.