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Interesting Circuit

Discussion in 'General Electronics Discussion' started by EnergyScavenger, Dec 15, 2013.

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  1. EnergyScavenger


    Feb 14, 2013
    I found an interesting circuit in the article found in figure 1d).
    (see link

    I tried to duplicate it with circuit simulator and with real components.
    Instead of MAX4684 chip, I used MAXDG307ACJ+-ND digikey.
    Instead of capacitor 33nF I used 47nF.
    On PC simulator I used DG303 and the circuit gives output as expected.
    However when I used real components, I am not getting two peaks (one positive and one negative)
    I have checked the chip and it works fine. It does not work when I use resistor and capacitor. My output is the same as input of signal which is 50% duty square waves at about 2 Hz. Am I missing something here? I have checked the circuit and it is layed out as in the drawing.:confused:
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    The MAX307 (not MAXDG307) is not suitable for this application. It is designed for signal multiplexing, not switching significant currents. The ON-resistance of each switch is typically 60 ohms, maximum 100 ohms at room temperature. That circuit has two switches in series for pulse to the relay coil, so there will be typically 120 ohms, maximum 200 ohms, in series with the coil on each pulse. This will greatly reduce the voltage available to the coil.

    The recommended device, MAX4684, has a total ON-resistance of 1.3 ohms maximum, and is rated for 300 mA carrying current.
  3. EnergyScavenger


    Feb 14, 2013
    Thanks for reply KrisBlueNZ.
    I ordered max4684 and see if that will work. I though that because of different chip I used, the capacitor and resistor values will be different. I didnt see much voltage drop on relay side.
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