lm1875 ic

Hi to u all,i recently build a circuit with tda 2050 for an old amplifier.the tdas work fine with split supplies of up to 25 volts but the amplifiers'transformer has a split supplies of 28 volts.a friend ask me to upgrade with lm1875 which has similar characteristics but can withstand a maximum of+/-30 volts and that the pcb is fine for the 1875.the problem is that upon switch on the 1 ohm resistor at the output (boucherot network ? ) of the 1875 burn out.what may be the problem?
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
upon switch on the 1 ohm resistor at the output (boucherot network ? ) of the 1875 burn out.what may be the problem?

I take it that this resistor is in series with a small cap of around 0.1uF. If so then the only possible cause of the burning is high frequency instability and oscillation.

Why is a different matter. You would have to check the application is suitable for the LM1875.... without looking up the relevant data sheets I don't know off hand what the differences are.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
I've just looked at the data sheets and there are no obvious problems that I can see. You would need to look at this with an oscilloscope and try and see what was happening. It may just need a small amount of compensation adding to the feedback network and/or perhaps a small output inductor adding.

All guesswork without a scope though I'm afraid.