Question

Design and draw voltage regulator to provide 4 to 10 V variable output voltage using IC 7812.

Answer 1

circuit diagram will look like as above.

Equation for finding output voltage is as

$R_2 = R_1 \frac{1}{\frac{V_{IC}}{V_{out}}-1}$

or it can be written as

$V_{out} = \frac{V_{IC}R_2}{R_1+R_2}$

Value of $V_{IC} = 12V$

Now for obtaining the output voltage 4-10 V we need to choose R₁ and R₂ such that we get the output.

If $R_2 = 5*R_1$ then V_out = 10V

If $R_2 = 0.5R_1$ then V_out = 4V