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opamp and voltage comparator???

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cool

New Member
o, do anyone tell me how to use LM741 as a voltage amplifer?? how to set the voltage gain???
and also, how to use LM331 as a voltage comparator??
HELP PLZ!!!!!!!!! :oops:
 

udi_hakim

New Member
The LM741 is ancient opamp there are a lot of variety of better opamps but the main idea stays the same.

The opamps differs one from other in their bandwidth , voltage , current , power consumption , number of amps in one chip , frequency response ...

National semiconductors are making grate opamps , ill show you how to use the LM324 https://www.national.com/ds.cgi/LM/LM124.pdf , its quad (4) operations amplifiers in one chip.

In the draw i attached i made a Voltage multiplier, it takes the voltage of Vi and multiply it in R2/R1 and invert it.

so Vo= - (Vi*R2/R10)
Remember that Vo cannot pass you VCC !!
 

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cool

New Member
o, thanks!! :)
when means by voltage to freq convertor??? then what is the function of LM311??
in fact, I would like to ues it for the IR receiver in order to filter out the noise after passing through a freq demodulator (LM567). :oops:
 

cool

New Member
Oh, thanks~
but i still don't know which circuit i should use to make L311 to be a comparator..... and how to set the center voltage??? :?
also, for the Op Amp LM741, I was fail to ues it as a voltage amplifier.... the output voltage is less then the input one.......I don't know what i did wrong... :cry:
 

Kev

New Member
Is this wot your trying to do?

Vin1 and Vin2 are you two voltages you want to compare
if Vin1 is greater than Vin2 Vout is positive
If Vin2 is greater than Vin1 Vout is negative
If Vin1 = Vin2 then Vout = 0V

sorry if i misunderstood.
 

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    vcompare.jpg
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