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AFarmer
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Join Date: Jan 2009
Posts: 32
Good Answers: 1

Inverting Op Amplifier

10/23/2009 10:48 PM

Hey guys I need help. I have a useable 3 to 5 Volts range for the input on the (-) inverting input. Pin 3 (+) is tied directly to ground of a 5v supply. What is needed is an output of 4.5 to .5 v. My op amp is suppose to work from rail to rail. Does the Op Amp need a load (maybe 10K)? I have read that some applications require Bias. How is this done? Any help is appreciated

AFarmer
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Mikerho
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#1

Re: Inverting Op Amplifier

10/24/2009 12:04 AM

First of all, what is the make and model of the op-amp?

Second, it would be extremely advantageous if you could provide a schematic of what you're trying to do. (You can insert graphic files into your post; .png, .gif, .jpg).

We will wait to see if you can provide more information.

Mike

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AFarmer
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#3
In reply to #1

Re: Inverting Op Amplifier

10/24/2009 11:45 AM

First of all, what is the make and model of the op-amp?

I will send it to an e-mail address if you will provide one

AFarmer
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maveric_manic
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#2

Re: Inverting Op Amplifier

10/24/2009 6:29 AM

Some op amps need a pullup to the +supply some are rail to rail. It would be helpful to know what op amp you are using and look it up at http://www.alldatasheet.com/

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AFarmer
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#4
In reply to #2

Re: Inverting Op Amplifier

10/24/2009 11:52 AM

First of all, what is the make and model of the op-amp?

Maveric--Thanks for the response- I am attempting to use MC33201P Mfg. by "ON"
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mjb1962853
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#5

Re: Inverting Op Amplifier

10/24/2009 12:48 PM

Supply voltage [+5V]
Input voltage range [3 - 5 V]

only DC input signal?
if AC signal, specify frequency range and gain

Output voltage range [0.5 - 4.5 V]

Source impedance or describe input device [___ ohms]
Output load or describe device connected to output of opamp [___ ohms]
(Should be larger than 100 ohms)

http://www.onsemi.com/PowerSolutions/product.do?id=MC33201

Lacking more specific requirements, I would "start" with a circuit similar to this sketch.
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AFarmer
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#6
In reply to #5

Re: Inverting Op Amplifier

10/24/2009 10:17 PM

Thanks mjb196283 for a good answer. I will connect my op amp per your suggestion and report results. Will try your bias. Still a newby to Op-Amps. Thanks

AFarmer
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AFarmer
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#7
In reply to #5

Re: Inverting Op Amplifier

10/27/2009 9:01 PM

mjb1962853--Thank you very much. It works very well! I had misunderstood how the Bias worked.

AFarmer
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mjb1962853
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#8
In reply to #7

Re: Inverting Op Amplifier

10/27/2009 11:56 PM

You are welcome. If you wish to learn more about op-amps, I suggest...

http://focus.ti.com/lit/an/slod006b/slod006b.pdf

Over 450 pages and IMHO a pretty good op-amp reference.

Best wishes.
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AFarmer (4); maveric_manic (1); Mikerho (1); mjb1962853 (2)

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