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Old 10th December 2003, 10:33 PM   #1
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Default Unbalanced Line Driver

I was just thinking about this earlier, is it this simple to make an unbalanced line driver? This should result in a 2X increase in voltage (say an input of 2V resulting in 4V) right? Do I need any other parts except for the cap to prevent the op amp from oscillating? What would be good op amps to use here, the standard NE5532, NE5534, Burr Browns, etc.?

Thanks.
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Old 10th December 2003, 10:36 PM   #2
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that won't work, as listed it isn't stable. a positive input voltage will create a positive output which is fedback. you need to attach to the negative terminal if you're going for an inverting amplifer.
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Old 11th December 2003, 12:34 AM   #3
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Thanks, I'm still trying to remember all my physics. It's been a while. So I should basically swap the connections on pins 2 and 3 right?
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Old 11th December 2003, 04:34 AM   #4
azira is offline azira  United States
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No, the non-inverting configuration is different than the inverting.

try this link:

http://www.leapfrogsw.com/noninverting.php3

your gain changes slightly, it's now 1+R1/R2 so you'll actually want to make your Resistors the same value.
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Old 11th December 2003, 01:40 PM   #5
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Thanks Azira, I was trying to make a non-inverting circuit, and the link you gave me helps me a lot. Thanks so much to everyone.
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Old 11th December 2003, 04:48 PM   #6
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Probably you mean this

However you have to put at least 2uF
at the input and your output
will be inverted.


Federico
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Old 11th December 2003, 07:26 PM   #7
azira is offline azira  United States
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Didn't ANYONE else make this mistake when they were learning about opamps? He's just trying to make a non-inverting opamp.

When they first teach you about inverting opamps you "pretend" the inputs are at the same voltage and then just sum currents and *poof* you have gain.

So the first logical step is to reverse the inputs and it should be noninverting... I mean.... they tell you after all that the + is the noninverting and the - is the inverting...

I thought everyone does this in school.... ok atleast I did

actually it's funny how if you use the simplification assumptions, it doesn't matter which terminal is + or - it still works out to be an inverting.
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Old 12th December 2003, 01:31 PM   #8
mskeete is offline mskeete  United Kingdom
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You'll need a low value resistor (between 100 ohms - 1K) in series with the output to keep the opamp stable
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