Hi All,
Happy New Year to you all. I have a question regarding the capacitors on either side of a voltage regulator. I have seen multiple schematics with different values. What are these values based on? How are the values calculated? Just wondering if the values are figured by trial and error AND an oscilloscope or is there a formula one uses to calculate them?



My circuit is for a vehicle application. I’ve seen this schematic for a vehicle and they use 100uF caps on either side. I have another schematic from Ford where they show them using 10 uF caps on each side and another schematic using 0.1 uF caps on either side along with a 10 uF cap on the input side and a 220 uF cap on the output side. Are they just connecting a basic voltage regulator to their intended circuit, using an oscilloscope and adding caps until they get the desired results?

The other thing I’ve seen is a Zener diode connected directly to ground as in the circuit above, but another circuit has a Zener going to a resistor and then to ground. Any reason why? I know you want to protect your circuit using the Zener, but is the resistor really necessary?

I’d like to make sure my circuit is properly protected, but don’t want overkill. What are your thoughts?

Thanks,
Tony