1.5V AA batteries - real voltage? Wireless thermostat.

Was that FETS? Those are a bit easier to push down in supply voltage, and I think that GaAs FETS can go even lower and are being pointed into really lower power digital s*it.

BUT, and its a big BUT. digital electronics seldom have more than two transistors in series - if you want to design - say - an op-amp you typically have 4,5 or 6 bipolar trannies in series and each one, if bipolar, needs half a volt or so.

There are very few op-amps that operate below about 7V total (+- 3.5V)

On 23/05/2023 16:10, The Natural Philosopher wrote: <snip>

I think that's a little out of date. Plenty will run at 3V3 single supply, and 2V7 isn't uncommon.

Decades have rattled by since you've touched anything electronic.

17 items there and that's the first catalogue in a google search for low voltage op-amps.

They are common place where low voltages are the norm where the highest power rail in a device is often +3.3V.

You do spout some nonsense.

Ah, you got there first. Great minds think alike!

It's CMOS MOSFETs. Threshold voltage on modern processes can be 0.3 - 0.5V, depending on your choice of transistor design.

In silicon you do - gates are more complex than simple NAND/NOR, so you tend to stack more MOSFETs.

And those are just the ones with Vdd_min = 3.3V - others go lower. eg this one works down to 2V:

Theo

That might be done with a transformer. The oscillator transformer in the diagram, might be the "charging" sound source.

This is a different technique, and one that, the more you do this, the "weaker" (less power) you can draw from the hot end. In other words, this technique might be suited if you needed a bias supply for something, but would work less well if you were trying to run a 600V motor or something. This technique was used on TV sets (perhaps just colour sets needing up to 25kV or so), and there's a potted module with all the HV components inside. I have one here, and it makes about 15kV or so. The voltage on a colour CRT TV set cannot be allowed to rise too high, because it surpasses the voltage where XRays are emitted :-)

And for modest voltages and purposes, a boost SMPS uses an inductor for voltage transformation. Sometimes circuits like this take the single cell Lithium storage in a portable electronics device, and develop 5V for a USB port with it (for USB charging purposes). There are more complicated versions of this, that are boost-buck and can produce any voltage on either side of the power source voltage (start with a 4V cell, make 3V or 5V from it, continuously adjustable).

Some circuits use boost, because it simplifies the power source. For example, people working with ultracaps, they will use only one ultracap (which has a pretty low max voltage), and then use a boost converter to make a useful power source from it.

Paul