Hello guys.

I plan on dropping 7v from a 12v car battery down to 5v to operate a sensor. The sensor requires a current of 6mA. So if my calculations are correct the 7805 will need to dissipate 42mW. I have a couple of questions:

1. If I use the typical circuit below:

Will I need the caps? Also, I can disregard a heat sink if only 42mW needs to be dissipated right?

Thanks.

 

one: Yes
two: Yes

 

In this instance what are the caps for if you don't mind me asking? I presume the 0.1 is to help smooth the output?

 

Hello,

The capacitor are there to prevent the regulator from oscillating.
It is a stability question.

Greetings,
Bertus

 

More precise 0.33u is required if the regulator is located more than 3" from the power supply filter. Will prevent regulator from oscillating. But I have never experienced a oscillating 7805 even in my most "quick and dirty" prototype boards. The 0.1u is the recommended minimum load capacitance to limit high frequency noise. I like to combine this with a 10U tantal cap

 

Nice, thanks for the replies guys.