Variable Voltage Regulator

253

03:54:23

Due to simulation glitch MOSFETs width must be manually turned up to 60um after starting the simulation.

Once MOSFET width is changed to proper value after starting simulation you can see that by altering the value of the zener diode one can change the voltage seen across the load. This set up can also be used as a constant current device when a known resistor is placed between the source and ground (commonly 1ohm or less) resulting in a voltage scale relating to current. The zener diode network may be replaced with a potentiometer with a small capacitor on it for noise stability.

published 11 years ago

Commodore64

11 years ago

Nice one. Thats whats basically inside most linear voltage regulators - except that the classic ones use bipolar transistors.

waynewec

11 years ago

Yeah, the most common use I see for discretely building these is rail splitters for op amp circuits. Otherwise I always just use a LM7xxx package.

Voltransistor

11 years ago

Why does it say "cannot find solution"?

waynewec

11 years ago

Make sure to turn down the width of the mosfet to around 1um before attempting to start the simulation. Then turn it up to around 60um after starting it. It's a wierd bug I've noticed but it works perfectly otherwise.

Voltransistor

11 years ago

That is a wierd bug. Thanks! And thanks for sharing.

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