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From: Lasse Langwadt <llc@fonz.dk>
Newsgroups: sci.electronics.design
Subject: Re: Ultra-Low Power Operation
Date: Mon, 7 Oct 2024 00:26:01 +0200
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On 10/6/24 16:35, john larkin wrote:
> On Sun, 06 Oct 2024 13:28:46 +0100, Cursitor Doom <cd@notformail.com>
> wrote:
> 
>> On Sun, 6 Oct 2024 09:25:47 -0000 (UTC), piglet
>> <erichpwagner@hotmail.com> wrote:
>>
>>> Cursitor Doom <cd@notformail.com> wrote:
>>>> Gentlemen,
>>>>
>>>> I vaguely recall going back the best part of 60 years now, there was a
>>>> competition among radio designers (AM in those days) to come up with
>>>> the design which would operate at the lowest possible supply voltage.
>>>> This had arisen, I would guess, as a result of the 'semiconductor
>>>> revolution' and all these designers would compete to develop a working
>>>> radio using ever more absurd Vcc levels. I'm pretty sure someone
>>>> managed to get something credible together that worked off of just
>>>> over 1 volt but can't be sure after all these years and there's
>>>> nothing I could find on the 'net about such a contest, either. But I
>>>> do remember it, for sure.
>>>> I'd just be interested to know what can be done with <1V today. Anyone
>>>> know?
>>>>
>>>
>>> Around that time there were published designs using germanium transistor
>>> inverter to step up 250-300mV to a few volts for driving more conventional
>>> items.
>>>
>>> Complete radios built from Ge tunnel diodes were done too.
>>>
>>> Silicon bipolars are constrained by 0.6/0.7V forward junction voltages but
>>> once started can continue stepping up from much lower voltages. LT made a
>>> boost converter IC that once started continued boosting from 100mV.
>>>
>>> Depletion fets let you go much lower, Jan Panteltje has posted his 20mV
>>> booster which lights a LED.
>>
>> I take your point, Piglet, but many of us still have Ge devices in our
>> junk boxes, so need not be constrained by the greater barrier height
>> of their Si equivalents.
>> Using some sort of boost converter is not in the spirit of this quest!
>> The circuits that were being submitted to the design contest were all
>> designed to operate straight from very low DC supplies, with none of
>> the shenanigans you mentioned. :)
>> This might be a tall order, but I'd like to see a circuit for an AM
>> radio which could be powered from half a volt.
> 
> Crystal sets need no power.

I remember an ancient popular mechanics that showed one made a coil a 
capacitor and an old razorblade and pencil to make a diode


> 
> There were some that rectified power from several stations to amplify
> one.
> 
> And yes, a depletion fet or one of the zero-threshold fets could
> detect and amplify at very low supply voltage.
> 
> Where can you buy a half volt battery?

a zinc and a copper nail in a lemon? ;)