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gain amplifier

aletropot

May 12, 2013
15
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May 12, 2013
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15
Hi all,

I need to duplicate the voltage of a pwm. when 0.1v should out 0.2v; 0.4v - 0.8v; 1v - 2v; etc...
Im using a non inverting op amp with a pot for adjustment, but it doesnt work like it should.
Like, when is 0.2v the out is 0.3v and when 1v is 2.4v.
I've tried with tl071 and lm324 and they behave differently, but both not correctly.
Any tips?
 

LvW

Apr 12, 2014
604
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Apr 12, 2014
Messages
604
Yes - my first tip: Show us the circuit.
If a circuit does not work - nobody can find the reason without knowing how it looks like.
 

duke37

Jan 9, 2011
5,364
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Jan 9, 2011
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5,364
Do the amps need a plus and minus power supply?

The gain will depend on the potentiometer setting.
 

GPG

Sep 18, 2015
452
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Sep 18, 2015
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452
Needs to be a rail to rail input/output amp
 

aletropot

May 12, 2013
15
Joined
May 12, 2013
Messages
15
Im asking because have checked on the datashet.
Plus on suggested applications the minus supply its connected to ground on all examples.
 

BobK

Jan 5, 2010
7,682
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Jan 5, 2010
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7,682
For a gain of 2 you need equal resistor for feedback and to ground. An LM324 should work okay as long as the supply is 2V greater than the max output you need. Here is a simulation. Note that below about 100mV the output will not be accurate because the op amp cannot output all the way down to 0V. If you need accuracy in that region, you will need a dual supply.

upload_2015-10-17_15-39-1.png

Bob
 

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aletropot

May 12, 2013
15
Joined
May 12, 2013
Messages
15
An LM324 should work okay as long as the supply is 2V greater than the max output you need.

It is, but I need accuracy on lower values, so to simplify I'll use a dual ps.
thanks all
 
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