LM7805 as Variable Voltage Regulator
Category: Linear Power Supplies
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is designed and simulated in Proteus 7.10. Therefore if you want to do simulation again you should have Proteus 7.10 installed in your computer or laptop. Functionality of this circuit is given below. 1. LM7805 is a fixed voltage regulator of positive 5V. But we can make it variable voltage regulator by doing little trick as you may have seen in the animation. 2. LM7805 is a simple 3 terminal/pin linear regulator. 1st pin is input, 2nd pin is ground (reference for output regulation) and 3rd pin is output. 3. LM7805 regulates 5V at output with respect to its 2nd pin (GND / Reference). But if we change its reference voltage as shown in animation, we can vary output voltage from 5V to Vin - 1.5V (its internal drop is almost 1.5V). 4. So, if you need some variable voltage, but you don't have a variable voltage regulator like LM317 and you just have LM7805 and some resistors fix or variable you can make a variable voltage regulator. Just download these files and do some experiments as you want.