positive response from noise input

Dec 23, 2014 4 Replies
C

Hello All, Making a project where I need to turn on a led when there is a glitch on my RF C.B. Most often the noise I receive is on the negative side (-100mv to -2v) as s een on the oscilloscope. I am using an opamp to amplify the voltage to usab le level. What I need to do is to invert the negative noise so I get the po sitive and negative voltage so I do do not 'miss' any spikes. I only use a 9v battery to power the opamp. I do not have a negative supply . Can someone give me an idea or direction to get what I am seeking



regards, Ken


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M

Is a glitch different from someone talking?

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C

Just a push on the CB will create a packet of noise, thats all I need. The problem is , most of these packets are below zero !

K
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P

AC couple it into a window comparator. Then you don't care about the polarity.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
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F

Ken-

Consider a peak-to-peak detector circuit. (This has the same configuration as a voltage doubler circuit.) Series capacitor feeds the junction of two stacked diodes. Output of top diode has a capacitor to ground. Choice of capacitors and load resistance determines the decay time of the output pulse.

One problem may be the forward bias voltage of the diodes. Germanium is lower than silicon, schotky may be better, but may still not be low enough for the -100mv signal. To get around the single supply, you might AC couple to an Op Amp input, and put the detector circuit on its output.

Fred

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