This is increasing an output voltage 78xx using a diode. The 78xx series are very cheap, popular. Although It is a fixed voltage regulator, we can change the output voltage level with many how.

A diode is a normal component in many stores, such as 1N4148 Diode. They have High efficiency and suitable for general uses.

While the electric current is flowing a diode in forward-bias. It has a voltage across that is very accurate, about 0.65V in each diode.

In the circuit above…

We add a diode Both diodes D2, D3 – 1N4148 in series, at between a common leg of IC1 and Ground. The output voltage will rise to about 0.65V + 0.65V = 1.3V every diode.

Suppose…

We use an LM7809 having the output voltage of 9V. Thus, the output of this circuit is 1.3V + 9V = 10.3 V.

Then, if we add another diode into 3 diodes. The voltage drop across on them of 1.3V + 0.65V = 1.95V.

So the output is 9V + 1.95 = 10.95V

We add a diode D1 to protect the regulator damaged of the output. It may have a feedback voltage come back from a load. The D1 is connecting in the reverse bias, it will absorb current spike to protects this circuit.

Next, we add 2 capacitors C1, C3 to filter out the transient noise. Which it can be induced into the supply by stray magnetic fields.

In addition, adding a capacitor-C2 drop across both diodes to improve a stability regulation. It will reduce noise at the output.

Convert 12V to 6V step-down voltage »

Note Another way to increase voltage up
Also, we can use a resistor or potentiometer to adjust the voltage output.
So it is easy and cheap.

• 7805 Adjustable voltage regulator
• Dual adjustable power supply

Or We use an op-amp to control a stable voltage regulator.
Variable regulated Power supply, 5V-13V using CA3140