Discussion in 'General Electronics Chat' started by chandann, Jul 2, 2012.

1. ### chandann Thread Starter New Member

Jul 2, 2012
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0
Hi,

Please suggest a circuit thru which i can add two phase shifted signal.

2. ### WBahn Moderator

Mar 31, 2012
17,777
4,805

What does the phase shift have to do with it, unless you are talking about "add" to mean something other than V1+V2.

3. ### chandann Thread Starter New Member

Jul 2, 2012
3
0
I tried with summing amplifier , it is not working for two out of phase signals. It works well for the two in phase signals .

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
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It often helps if you post a schematic of what you have already tried.

5. ### WBahn Moderator

Mar 31, 2012
17,777
4,805
When you say it isn't working for two out of phase signals, what do you mean? What do you expect to see? What are you actually seeing?

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
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This one works for me OK ...

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7. ### chandann Thread Starter New Member

Jul 2, 2012
3
0
I was expecting zero or almost zero o/p signal with 2 out phase signals & of same amplitude at the input. Am getting o/p as if the circuit is connected with any one i/p to 0V. & one more input to say sme 200mV~.
&
the circuit is same as the attached in the above post. Except that am using single supply op-Amp so giving vcc/2 voltage as vref to +terminal of OP-AMP.

Thank you all.

8. ### WBahn Moderator

Mar 31, 2012
17,777
4,805
Is this in simulation or with actual hardware?

What do you mean by "out of phase"? Just two phases that aren't equal? 180 degrees out of phase? 90 degrees out of phase? What?

How big are the two input signals?

If you are using a physical circuit and are putting in one signal that is, say, 5V in amplitude and the other one is 5V in amplitude but out of phase by 180 degrees, then I would expect zero or near zero output. But what you describe sounds pretty much like that -- the output looks like one input is 0V and the other input is 200mV. Thus, I suspect that if you adjusted one of the input signals up (or possibly down) by just 200mV, you will see your "near zero" output condition.

If that's the case, what might be happening?

How sure are you that the amplitudes of your two input signals are actually the same?

How perfect are your input resistors? What if one of them is, say, 5% larger than the other?

9. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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Do you mean either of the options shown in the attachment? The left hand form won't work.

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