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djmanning
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Join Date: Mar 2009
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Design a 741 op-amp

03/07/2009 2:17 PM

A balanced 3-phase WYE power system operates at 50 Hz. The magnitude of the line-to-line voltages is V21 = V32 = V13 = 110V rms. Design an instrumentation system to monitor the voltage, V21 and yeild an output voltage, Vo, given by the equation, Vout = .1V21. Use 741 op-amps and Rin must be greater than 100M ohms. Select the proper value of Vcc for the 741 op-amps?
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bhankiii
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#1

Re: Design a 741 op-amp

03/07/2009 9:58 PM

yeah, and?
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rcapper
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#2

Re: Design a 741 op-amp

03/08/2009 12:29 AM

Infeasible.

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sb
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#3
In reply to #2

Re: Design a 741 op-amp

03/08/2009 1:00 AM

And homework

look at the language .

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sb
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#4

Re: Design a 741 op-amp

03/08/2009 1:04 AM

Put a voltmeter between lines 2 and 1 and keep on reading this every 10 seconds (that is monotoring the voltage)

Put at transformer ratio 10:1 rated Pri 110 V (KVA? - I don't know) across lines 2 and 1 , This will give Vout = 0.1V21

Don't need OPAMP or R throw them out (sorry dispose them ICs create environmental hazard if not properly disposed)

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GW
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#5

Re: Design a 741 op-amp

03/08/2009 1:51 AM

Home work problem.

Hmm, lets see, pick a resistor greater than 100M, oh gosh, what are the standard values? Gain .1? Thats just .1 x my first choice! DC output? Why not rectify? reference everything to ground and away you go. Needs a few didles for the Ac to DC rectify and average, but that just falls out of the numbers. Proper value for Vcc? why, now we need the spec sheets. Oh darn, the dog ate them.
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user-deleted-1105
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#6

Re: Design a 741 op-amp

03/08/2009 3:52 AM

If I do it ...do I get a degree?
Del

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CJMcGill
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#7
In reply to #6

Re: Design a 741 op-amp

03/08/2009 3:57 AM

Maybe a temperature, but not a degree.

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Isti80
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#8

Re: Design a 741 op-amp

03/08/2009 8:49 AM

Can you rephrase yourself or your question?

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Sleddriver
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#9

Re: Design a 741 op-amp

03/08/2009 11:02 PM

Sounds like homework to me!

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Goodho
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#10

Re: Design a 741 op-amp

03/09/2009 6:00 PM

Do your own home work! Part of engineering is discovering and proving what will not work. You will see more of that than you can imagine
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Isti80
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#11

Re: Design a 741 op-amp

03/10/2009 5:46 AM

Looks like no one is helping you out much here but in all honesty your question isn't good enough.

To begin with Rin > 100M ohms; have you checked the spec on 741 op-amp?

you'd better write a program for a microcontroller to generate this type of power requirement as accurately as you described it here.

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sb
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#12
In reply to #11

Re: Design a 741 op-amp

03/10/2009 9:59 AM

How can he ? The homework is using 741

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Isti80
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#13
In reply to #12

Re: Design a 741 op-amp

03/10/2009 1:20 PM

sorry.

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sb
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#14
In reply to #13

Re: Design a 741 op-amp

03/10/2009 11:44 PM
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Isti80
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#17
In reply to #14

Re: Design a 741 op-amp

03/11/2009 7:08 AM

Most likely prehistoric.

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sb
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#18
In reply to #17

Re: Design a 741 op-amp

03/11/2009 9:59 AM

I remember using IC 741 during engineering. Sometimes it feels nice to hear those names IC 741, recently IC555 also came up.

Must be from some control design book published in 70s and not updated hence (Revised edition of the originals printed in 1971. Only preface and $s changed)

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rcapper
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#15
In reply to #12

Re: Design a 741 op-amp

03/11/2009 1:26 AM

Anyway, why would anyone still use a 741? How old is that textbook?

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GW
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#16
In reply to #15

Re: Design a 741 op-amp

03/11/2009 1:42 AM

Its been a while, but I thought they brought in a "741" that had fet inputs, or at least one that had similar characteristics. No matter, with the high input volts a regular 741 should still be usable with such low net gain required.
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