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
can you throw some suggestions on this,
please email me : arasukumar@yahoo.com
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
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
- Status
- Not open for further replies.