7905 Basic Circuit Diagram
Here is the image showing the basic usage of 7905 IC, you can see that a 1uf capacitor is used at the input to filter the noise. Make sure that capacitor voltage is more than the input voltage. Another 10uf capacitor is used at the output to further refine the output current. Input voltage can be anywhere between 7v to 25V. If you have a small load then you wont need a heatsink plate. However for 1A or above loads, you should attach a heatsink plate. The maximum allowed current is 1.5A.
Safety Features: 7905 has built-in overcurrent and short circuit protection features. These features can kick in once the maximum allowed current is reached. It also has a documented thermal protection against overheating but beware that operating the IC near its maximum temperature can potentially alter its dye structure resulting in unpredictable behaviors. I certainly don't recommend you to put a continuous load of 1.5A on it for a long time, instead if you have a bigger load, you should probably look into the parallel use of 7905.
Parallel Use of 7905 Although it is not officially mentioned anywhere but in reality, I have successfully used two or more 7905 in parallel. Theoretically, no two 7905 can give exact same output voltage, so the one which gives more voltage will try to take more load and will be throttled later putting all the load to the other one which will then be throttled too. This can result in a never-ending loop but we can overcome this by adding a low value but high-power resistor at the end of each voltage regulator. This will counter correct the small voltage differences between both regulators and will more evenly balance the current between them. Technically we can get close to 3A current from two 7905 ICs if attached as shown in the image. A small amount of current is wasted as heat in the resistors but its not very noticeable. Please note that in our circuit, we soldered both 7905 very close to one another. Therefore we only two capacitors are used at the combined input and output of both regulators. Please try to fit the regulators as close as possible, in case of a 3 inches of or more gap, please use individual capacitor for each regulator IC.
Posted or Updated On:Mar 29, 2021