gyrator doesn't work?

donovas

Member
2014-06-22 6:45 am
could somebody explain this circuit to me?

i've p2p,ed it with only 24v input voltage, feeding a simple zener shunt that feeds an opamp, and with the default resistor values it only outputs 1v ish :eek:

so i'm thinking of lowering r1 value and perhaps r2 but i don't know how to go about figuring out the exact value...

the opamp is only about 70ma load.
 

rayma

Member
2011-04-29 8:37 pm
for the neg supply i'm using 9610. i've ensured the polarity/pinout of the components multiple times.

Try loading it with a resistor instead of the Zener. Try connecting the cap to ground instead of the load.
If still bad, try adjusting the 33 Ohm resistor. Or maybe one of the parts are bad, the FET? http://web12491.serv4.spacequadrat.de/html/B1+_gyrator.pdf
There's a thread also. http://www.diyaudio.com/forums/power-supplies/155657-mosfet-gyrator-using-irf840.html
 
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Is the zener voltage 15v (ZD15)? If so, R1 needs to be much smaller to provide enough current to get the zener diode to 'zener'. Most zeners need at least a few mA of current. So R1 needs to be 24-15/2mA or 4.5k (for 1mA, R1=9k). A TL431 has a similar min operating current. An op-amp based gyrator might give better results.