HiFi preamp LME49720 - amplification 10x?

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#41
PRR said:
> Is power transformer 15V with 200mA for LME49720 enough?

Did you read the datasheet?

Look at page 5, IOUT and IS. 12mA to live. 20+mA of load current, if needed, but in audio less than half the time. So 20mA max per chip. 40mA for stereo. Double the DC current to shop for an AC Amps rating. 80mA. You may find that you can't buy a respectable transformer that small.
Click to expand...

Thank you, now I understand what to check in data sheet next time.
 
#42
MilanAudio said:
2) I have for amplification R3 / R2 + 1 values 10000/680. Why higher resistance is usually used? What will happen if the resistors will be just 100/6.8?
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Another very good question and that's addressed in nearly all authoritative literature. Earlier, I mentioned Walt Jung's Op-Amp Cookbook. Carefully read the first few chapters. There are many other good sources too, not only Jung. Another good source are the op-amp manufactures' application notes.

In a nutshell, more or less, the choice of low or high resistor values is a tradeoff between several factors that come down to stage noise, input offset current management, and circuit layout leakages.
 
#44
rfengineer said:
Another very good question and that's addressed in nearly all authoritative literature. Earlier, I mentioned Walt Jung's Op-Amp Cookbook. Carefully read the first few chapters. There are many other good sources too, not only Jung. Another good source are the op-amp manufactures' application notes.

In a nutshell, more or less, the choice of low or high resistor values is a tradeoff between several factors that come down to stage noise, input offset current management, and circuit layout leakages.
Click to expand...

Book is downloaded and ready for reading before sleep :yes:
 
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