reference voltage of voltage regulators

Hi
What is meant by reference vooltage of voltage regulator?

•Voltage regulators work by gauging the actual voltage output of a device against a reference voltage inside of the device. If there is a difference between the actual voltage and the reference voltage, that difference is amplified and used to reduce voltage errors. The more stable a voltage regulator is, the slower it is to respond. This is because of the regulator is either increasing the gain of the input on the device or lowering the gain of the device at the output level. Some regulators will shut down the device they are installed in if the current draw exceeds a certain level.

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In electronics, a linear regulator is a voltage regulator based on an active device (such as a bipolar junction transistor, field effect transistor or vacuum tube) operating in its "linear region" (in contrast, a switching regulator is based on a transistor forced to act as an on/off switch) or passive devices like zener diodes operated in their breakdown region. The regulating device is made to act like a variable resistor, continuously adjusting a voltage divider network to maintain a constant output voltage. It is very inefficient compared to a switched-mode power supply, since it sheds the difference voltage by dissipating heat.

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Linear regulator - Wikipedia, the free encyclopedia

A voltage regulator has to use an internal reference voltage (which is generated from the input voltage),
it compares that voltage to the input voltage and depending on the result of this comparison it changes the pass element drive to adjust the output (linear regulator).

For example in the following 2 circuits the reference voltage is generated using the zener diode.


Alex