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deepika97
Joined: 19 May 2008
Posts: 1
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 19 May 2008 17:35 reg: square wave to sine wave converter |
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Hi,
I am working on a feedback circuit. I am using a sinusoidal signal to excite a sensor. I need to control the output voltage in the range of 100-200mV. So I am working with an AGC cirucit which is a real complicated one. So I have thought of using a simple diode clamping circuit for this but as it generates a square wave. I need a sine wave to be fed back to the sensor for the excitation again since the square wave gives spurious frequencies. I am operating my circuit around 1K-500KHz. If it would be great if anyone can suggest a simple circuitry with couple of opamps, resistors and capacitors.
Regards,
Deepika
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Sinisa
Joined: 03 Mar 2003
Posts: 337
Helped: 66
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19 May 2008 18:14 Re: reg: square wave to sine wave converter |
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| AGC cicuits should not be too complicated, and it very likely best choice for you. Triangle to sine shaping with resistor/diode networks is done in a lot off signal generators, just search for manuals with schematics on the net for example. I think this might be more comlicated than building AGC.
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zeeshanzia84
Joined: 29 May 2006
Posts: 202
Helped: 19
Location: Pakistan / Germany
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19 May 2008 18:16 Re: reg: square wave to sine wave converter |
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use a low pass filter
the sharper edges of the square wave are due to the higher frequency components...so as you remove them, you get a smoother and smoother waveform.
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FvM
Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany
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19 May 2008 18:23 Re: reg: square wave to sine wave converter |
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| I don't exactly understand what's your starting point. If you have a sine signal originally, I would use an analog multiplier or a JFET/MOSFET as controllable resistor. If it's a square wave, filters as suggested should help.
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LvW
Joined: 07 May 2008
Posts: 1466
Helped: 242
Location: Germany
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19 May 2008 21:43 Re: reg: square wave to sine wave converter |
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As mentioned in both contributions above, filtering the squarewave with a lowpass (or bandpass) is the most direct way to produce "something like a sinewave". The required filter order depends on the desired quality of the sine wave (THD).
However, this method works only for a fixed frequency.
Another - a bit unknown - method uses the classical differential amp (longtailed pair) to convert triangle waves to sine waves. This is in a broad frequency band independent on frequency, however, this method works only for a fixed amplitude.
Example: for an amplitude of 80 mV you get a sine wave with a THD of app. 1.5%.
Disadvantage: The squarewave has to be converted to triangle before (Integration)
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lladnar23
Joined: 20 Mar 2006
Posts: 221
Helped: 32
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20 May 2008 7:55 reg: square wave to sine wave converter |
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| Yea - for the most part, there are two main approaches: lowpass or bandpass filtering to remove harmonics, and "shaping" a triangle wave with diodes, etc..
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