The linear voltage regulator basically consists of input, output and GND pins. Since it has the characteristic of variable output, a feedback pin that feeds back the output voltage is added.
The internal circuit of a linear regulator basically consists of an error amplifier (an operational amplifier for error detection), a reference voltage source, and an output transistor. Although PCH MOSFET and NCH MOSFET are used as output transistors, bipolar PNP and NPN transistors can also be used.
Operation is fully simulated, using one of the basic control circuits of the operational amplifier, the feedback loop. After the input or load changes, the error amplifier continuously compares the feedback reference voltage from the regulator's output voltage, adjusts the power transistor to zero, and keeps the VO constant, even if the output voltage begins to change. This is the feedback loop that controls stabilization (regulation).
As mentioned earlier, the voltage of the non-inverting pins of the error amplifier is usually the same as that of the VREF, so the current to R2 will be constant. The current flowing to R1 and R2 can be obtained by REF÷R2, so Vo will be current ×(R1+R2)