Resistor gets too hot

ian field

Joined Oct 27, 2012
6,536
Sounds like the amplifier may be oscillating.
Possible, but BTL amplifiers tend to be more forgiving about deficient supply decoupling.

I'd start by checking around the input pins. The datasheet suggests its DC coupled all the way through - any offset on the inputs could produce a large voltage differential on the outputs.
 

Thread Starter

Bigbizkit

Joined Oct 29, 2015
44
Hello,

The test circuit shows 0.12μF capacitors with 2.2 Ohm resistors:

View attachment 111987

You are using 0.22 μF and 10 Ohms.

Bertus
Argh! I cant fix this prob, so my next option is to make a new pcb and use this test circuit schematic since i cant find other ta8205 amp design on the web.
What do you think guys?
Ya think the test circuit is good?
 

ian field

Joined Oct 27, 2012
6,536
Update:
Oh! Problem solved! I replaced the 224 caps with 104. Burnt resistor no more!
Those 10R resistors in series with capacitors aren't being cooked by DC.

Someone else suggested it could be oscillating - I observed that BTL are fairly tolerant of weak supply decoupling.

To break that down a bit - you don't need huge electrolytics with BTL, small ish ones are adequate. The BTL draws Vcc current on both the positive and negative half cycles - it actually the bits between the half cycles that don't draw current that can be a problem.

The current fluctuation is double the audio frequency, the reservoir electrolytic probably needn't be any bigger than about 100 - 220uF, but you need to parallel some low capacitance with low ESR - another use for the 224 caps that became redundant.
 
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