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Subject: Re: Request: very low power receiver/ AM detector

Date: 04/03/00 at 9:14 PM
Posted by: Terry Moreau
E-mail: tmoreau@direct.ca
Message Posted:

In Reply to: Re: Request: very low power receiver/ AM detector posted by John Dunn - Consultant on 03/23/00 at 11:54 AM:

I love a question like this!

Actually, using a couple bipolars. like the 2N5087, even at collector currents of 10uA, you can use positive feedback to get enormous values of gain!

Another way is to use a cmos inverter like the 4069, control or regulate the voltage between V+ and GRND to get a suitable quiescent current, and cascade stages, also possible to use positive feedback to boost AC gain.

For 455Khz, I would be inclinded to use a ceramic resonator. Actual detection could be a diode, or even just an invertor biased to select just the positive half of the waveform and dump this into an averaging capacitor resistor network. I would expect that either way, 2 Volts, at 100 uAmps of current would not be at all unreasonable to acheive. I've done this sort of thing before without difficulty. Lower current draw than this may become a challenge but should still be possible....getting below 10uA may start to become a little unreasonable at that frequency, though you might have some luck using the 74HCU04 inverter, and run it at only 1.5 volts.

Let us know how you make out!

Terry Moreau :-)

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