There are electronic components like microprocessors which work at 1-2V.

  1. Why do some semiconductor devices have a minimum voltage requirement?
  2. Are there (simple) microcontrollers which work at few tens of millivolts or less?

BJTs (bipolar junction transistors) require forward-biasing a diode junction to operate. That inherently requires a minimum voltage. That voltage depends on the material and temperature.

Just being able to turn transistors on and off isn't good enough by itself. The result of those on/off control signals have to actually do something. That's going to require some additional voltage swing.

Often the point is to produce a voltage signal. That signal has to have some swing to be useful.

MOSFETs (metal oxide semiconductor field effect transistors) work on a principle that is somewhat "soft". There is no hard transition at a particular gate voltage. If there isn't enough voltage range to swing the gates over, then the devices won't be solidly on at one end and solidly off at the other end.

Lower supply voltage reduces the charge that has to be transferred each time the gate is switched, but also increases quiescent current due to higher off-state leakage.

Modern processors do run at low voltages, like as low as 1.2 V, but it's a constant tradeoff between switching charge and leakage. There was one Intel processor some years ago where about half the average power was due to leakage current when the MOSFETs were in the off state. The leakage of one transistor might be very small, but this adds up due to lots of transistors. A nano-Amp here, a nano-Amp there, and pretty soon you're talking about real current.


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