This is increasing output voltage 78xx using 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 Diodes. They have High efficiency and suitable for general use.
Circuit diagram of increasing output voltage 78xx using diode
While the electric current is flowing a diode in forward-bias. It will have a voltage drop across that is very accurate, about 0.65V 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. When the output may have feedback voltage come back from a load. The D1 is connecting in the reverse bias, it will absorb current spike to protects this circuit.
Two capacitors C1, C3, we add them 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.
Note Another way to increase voltage up
Also, we can use a resistor or potentiometer to adjust voltage output.
So it is easy and cheap.
Or We use an op-amp to control a stable voltage regulutor.
Variable regulated Power supply, 5V-13V using CA3140
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