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the right op amp?...

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is the lm358 good to amplify the signal from a mic and then use the other opamp in the ic as a comparator so that it gives a logical HIGH when the signal level increases to some desired value?? would that work

i chose the lm358 purely since it is widely available
 
is the lm358 good to amplify the signal from a mic and then use the other opamp in the ic as a comparator so that it gives a logical HIGH when the signal level increases to some desired value?? would that work

i chose the lm358 purely since it is widely available

As long as you have no concern about quality it would be OK, but don't forget you probably need to rectifiy the audio signal to use a comparitor on it.
 
aa yes
what ia m trying to do is to gain a siganl from a mic, and when the siganl is large enough i get a logic 1 from the comparator... don't really need a high quality sound amplifier.. i only hope that the lm358 is suitable to give a high enough gain to the mic signal so that it can be easily compared to some refernece voltage in the comparator section...

what do you think, would the lm358 fit?

thanks
 
Your mic preamp might need a gain of 200 or more.
The LM358 cuts high audio frequencies when its gain is set to more than only about 30. Also it is noisy which might be detected by your comparator.

The article from Texas Instruments has a non-inverting opamp circuit that will not work.
 

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hmm.. it is turning out to be a problem then to find an opamp with single supply low voltage (5V max) available and suitable for the job.... :(
 
hmm.. it is turning out to be a problem then to find an opamp with single supply low voltage (5V max) available and suitable for the job.... :(

hi,
Whats your location.?
 
hi,
Whats your location.?

Malta.. the problem is that the shop's database is not that good... i can always buy from ebay yes but that would take ages until the packet arrives... i would have to phone every time i get some ic number...

any other part numbers qualifying to my requirements? thanks
regards
 
There are thousands of opamps available that are made by about 30 manufacturers. We don't know what you can get and what you cannot get.
Most of us can get any of them.
 
Quote:
Originally Posted by Nigel Goodwin
Try reading the 'sticky' at the top of this very forum.

hi nigel, i saw the sticky note diagram...thanks a lot, one last question just to make sure... the single supply technique shown in the diagram is for when one needs to use only a single supply and the op amp is made to work with dual supply right?

thanks
 
Quote:
Originally Posted by Nigel Goodwin
Try reading the 'sticky' at the top of this very forum.

hi nigel, i saw the sticky note diagram...thanks a lot, one last question just to make sure... the single supply technique shown in the diagram is for when one needs to use only a single supply and the op amp is made to work with dual supply right?

Yes - except ALL normal opamps are made to work with split supplies, even the 'single supply' ones.
 
Yes - except ALL normal opamps are made to work with split supplies, even the 'single supply' ones.

I think of this another way. All OPAMPs have a Vdd and a Vss pin. To power them, you need to connect them such that Vdd-Vss > VPmin (minimum power supply voltage), where VPmin is specified on the data sheet. Only a subset of all OPAMPs have a VPmin at 5V or less. Most older OPAMPs dont work well unless VP is >10V.

It is your choice as to how you configure the power supply. It can be a single voltage source, or it can be two voltage sources in series. If the former, you can define your circuit ground at either of two places, Vdd or Vss.
If the latter, then you can define your circuit ground at any of three places, Vdd, Vss or the tap between the two supplies.

Each configuration has applications. It is up to you as the circuit designer to figure out which is best for your specific application.
 
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