Is this just diode noise?

Feb 01, 2016 3 Replies
A

Hi all, I'm working on a circuit to test LC ferrite antennas. I found the amp output very noisy with the rectifying diode in the circuit. I can hear the noise and measure it on my meter. Very little noise without the diode. See the link below for a block drawing of the circuit with and without the diode.



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Is it simply the diode noise, or something else?


Thanks, Mikek



PS, while receiving a local station, with a tuned LC driving the input, I can get 2v on the meter, although it is over driving the LM386.


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T

Do you have a DC path to ground at both ends of the diode?

You may be running the amplifier chain effectively from an open circuit.

-TV
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A

I don't. I'll try a resistive load. I suggest there is some type of impedance on the input because when it's open the output hits the positive rail. There is no reason I can't load the diode, I have a high input impedance

50 ohm output amp that is between the LC and the diode.

Thanks, Mikek

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A

I put a 100k resistor from the diode cathode to ground, it dropped the noise measurement from 330mv to 102mv. Probably will even get better when I tighten things up.

Thanks, Mikek

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