tda7250

arasuk · 21st January 2004, 02:03 PM

Hi i have done the tda7250 amp with the out put tranisistors as mj11015/16 , and i am facing the problem like the amp will get quite hot even at no load or no signal input , works fine if i raise volume but the heat is i feel some thing wrong , probably the amps osillating,

can you throw some suggestions on this,

please email me : arasukumar@yahoo.com

IanHarvey · 22nd January 2004, 04:19 PM

The TDA7250 chip does tend to run quite a high bias current; it's possible that it's just working properly.

I assume you don't have access to a 'scope; obviously, this would easily detect oscillation. Otherwise, you will need a multimeter to measure (a) the supply current and (b) the voltage across the sense resistors in line with the collectors. The data sheet says (b) is about 20mV, giving ~130mA quiescent current per channel (i.e. about 0.25A for the whole amp).

If this is what you measured, it might be just insufficient heatsinking. If it's more than this, or the currents don't seem to add up, oscillation could be the cause. Another sign of oscillation is a lot of noise at the speaker output, especially if it sounds "rough", or like a detuned AM radio...

Cheers
IH

21st January 2004, 02:03 PM	#1
arasuk diyAudio Member Join Date: Dec 2003 Location: bangalore	tda7250 Hi i have done the tda7250 amp with the out put tranisistors as mj11015/16 , and i am facing the problem like the amp will get quite hot even at no load or no signal input , works fine if i raise volume but the heat is i feel some thing wrong , probably the amps osillating, can you throw some suggestions on this, please email me : arasukumar@yahoo.com

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22nd January 2004, 04:19 PM	#2
IanHarvey diyAudio Member Join Date: Apr 2003 Location: Cambridge, UK	The TDA7250 chip does tend to run quite a high bias current; it's possible that it's just working properly. I assume you don't have access to a 'scope; obviously, this would easily detect oscillation. Otherwise, you will need a multimeter to measure (a) the supply current and (b) the voltage across the sense resistors in line with the collectors. The data sheet says (b) is about 20mV, giving ~130mA quiescent current per channel (i.e. about 0.25A for the whole amp). If this is what you measured, it might be just insufficient heatsinking. If it's more than this, or the currents don't seem to add up, oscillation could be the cause. Another sign of oscillation is a lot of noise at the speaker output, especially if it sounds "rough", or like a detuned AM radio... Cheers IH

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