Ultra-Low Power Operation

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.

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 potato battery is around that.

You're mixing up low power with low voltage.

Many RF devices are available today (and were available in the past) that operate without a battery.

Low voltage is energy scavenging territory. Google it.

RL

Arguable. They don't need batteries, but do need the power of the transmitter to produce an output.

Really? Good Lord! I've never heard of that; most resourceful!

Fascinating. Thanks for that. Depletion mode? I'll have to re-acquaint myself with that. I normally use enhancement mode FETs for anything requiring the preservation of a high Z signal. I'm not even sure what the typical application for a depletion mode FET might be.

You can't buy them, but I have very many of them here, actually. I keep forgetting to recharge them. :)

Depletion fets are very useful. The Supertex parts are great. I use them as current limiters, for driving LEDs or zeners or discharging caps.

They are great as input protectors too. See AoE3 p 361. H+H added the source-source resistor.

The LND150/250 parts have very repeatable Idss, around 1.6 mA. Jfets are all over the place with as much as 10:1 Idss specs.

Somebody, can't remember who, makes zero-threshold mosfets.

We need a giant class-action lawsuit against people who sell batteries that corrode and leak and destroy things.

Am I?? How so?

For instance....?

I don't Google *anything* if it can possibly be avoided.

Back in the cold war days some surveillance bugs used that technique to avoid having to break in to replace power cells! Maybe some still do.

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

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

There are quite a lot of such combinations you can use. Safety pins, lightbulb filaments and copper plated pennies that have been baked for example.

Again, lots of ways to make batteries. We found all this fascinating when we were children, but kids today just don't seem to give a damn about it.

Your subject line says "low power" and your content talks only about low voltage operation. You explicitly reject the energy scavenging approach that uses inverters to boost low voltage sources up a voltages that can operate a silicon transistor.

If you read any of the electronic trade journals you wouldn't need to google it. You don't, and using google would rub your nose in the fact that you ought to, if you are posting here.

In reality you prefer to waste your time on sources that supply the lying misinformation that makes you happy - like Zero Hedge and Russia Today.

or thermocouples, but you need quite a few in series to get 500mV

On 10/6/24 10:19 AM, john larkin wrote: <...>