Help needed for Phase Sensitive Detector circuit

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#1 21661032 02 Feb 2012 04:34

John Savage John Savage

Anonymous
Post #1
21661032 02 Feb 2012 04:34

Can someone pleass take a look at my circuit and tell why it isnt working? I took it from a book and not sure about the switching part of it.
A recommended PSD circuit would be very helpful.
Thanks in advance.

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#2 21661033 02 Feb 2012 08:57

DAVID CUTHBERT DAVID CUTHBERT

Anonymous

Post #2
21661033 02 Feb 2012 08:57

John,

the input signal and the sync oscillator, or frequency reference, must be the same frequency but can differ in phase. Are they the same frequency?
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#3 21661034 02 Feb 2012 10:58

John Savage John Savage

Anonymous

Post #3
21661034 02 Feb 2012 10:58

The input signal is 50HZ and the 555 timer reference is 50.2787 Hz at a duty cycle of 58.2 %. I have attached the transient graph for 10 seconds. Can you see what is wrong?
#4 21661035 02 Feb 2012 11:31

DAVID CUTHBERT DAVID CUTHBERT

Anonymous

Post #4
21661035 02 Feb 2012 11:31

The waveform looks reasonable given a frequency offset of 0.2787 Hz.
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#5 21661036 02 Feb 2012 15:28

John Savage John Savage

Anonymous

Post #5
21661036 02 Feb 2012 15:28

I should getting a full-wave rectified output that would be smoothed out by the LPF.
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#6 21661037 02 Feb 2012 18:36

DAVID CUTHBERT DAVID CUTHBERT

Anonymous

Post #6
21661037 02 Feb 2012 18:36

The circuit does a differential to single ended conversion then applies this to the phase detector. The output does exhibit a DC component of 250 mV.

The phase detector integrator has a 22 ms time constant and that will not show up on the oscilloscope scale you used.
#7 21661038 02 Feb 2012 18:58

John Savage John Savage

Anonymous

Post #7
21661038 02 Feb 2012 18:58

Not sure what you mean.
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Help needed for Phase Sensitive Detector circuit

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