[AMRadio] infinite impedance detector vs diode

John Coleman jc at pctechref.com
Thu Sep 4 08:59:39 EDT 2008

The way I understand it, 

The infinite impedance detector is a device such as a tube or FET that
normally draws output current unless reversed biased.  The device is
reversed biased to cutoff and then input signal turns it on like class B
service but the input does not draw current.  The output is taken from the
cathode, or source in the case of a FET, in follower fashion.  

I am not sure how this is going to correct the slew distortion that is
caused by the RF filtering and discharge rate of the output.  Perhaps it is
because of the follower effect of having a low Z output with no diode at the
output.  This may mean that the discharge is at the same rate as the charge?

I'd be interested to see what you come up with Jim.  There are several
circuits on the internet (Google "infinite impedance detector").  I have
never played with this.

John Coleman, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Jim Tonne
Sent: Wednesday, September 03, 2008 7:56 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] Diode demodulator appnote

Agreed.  Send me a schematic of such and I will see if I
can run it through the analysis routines.

- Jim Tonne   WB6BLD   TonneSoftware.com

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