7805 regulator question

Dec 18, 2004 2 Replies

There was not enough explanation on the spec sheet for me to understand its full workings: How high an input voltage do I need to ensure 5 volts out? E.g., will it output 5 volts if the input voltage is 5.5 volts? What volage figure tells me the minimum input voltage?



Also, if the DC in is clean, will the DC out be clean?



Ken (to reply via email remove "zz" from address)



According to the data sheet at: http://www.fairchildsemi.com/ds/KA%2FKA7805.pdf , 7V

For a 7805, the datasheet recommends 7 to 20V.

The point of the regulator is to 'clean up' the output. However, if the input dips below 7V, the output will reflect that.

One tip in the datasheet is to use a capacitor on both the input and the output. A 0.33uF on input, and a 0.1uF on output is customary.

Regards, Robert Monsen "Your Highness, I have no need of this hypothesis." - Pierre Laplace (1749-1827), to Napoleon, on why his works on celestial mechanics make no mention of God.

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required