More low hanging fruit

[saturated]

This looks pretty simple but I wanted to try it

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I did not find a 7505 but I did have a 7808ct so I hooked it up and went with it

Looks like I forgot about having the capacitor close 

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And the predictable results (I hope  )

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It still was an eye opener seeing DC voltage appear at the output before the minimum input level

I wondered if the results might be wacked without a load resistor

Also at the end I felt the metal tab with my hand but it wasn't hot


Next I have to add some resistors and do some more stuff

Hmm now I hope these results agree with the data sheet 

[joecool85]

Those numbers look good.  It will have some output voltage below minimum input spec, it just won't be super consistent and also will be well below your desired 8v output.

[saturated]

Yes sir thanks always nice to hear from

DA BIG BOSS

 

[J M Fahey]

I guess those low voltages are parasitic/leaks.
You read them only because multimeter has very high impedance.
Try loading output with, say, a 1k resistor and remeasure.

[saturated]

Yes sir thanks

And the results are in

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I did try to feel the resistor and the heat sink tab to see if it was getting warm but not really

[Kaz Kylheku]

Yes, a linear regulator isn't something that gives 0V if it is not able to provide its stated voltage. That is a behavior we could design in, but it would actually be unhelpful to downstream devices. Some digital stuff is able to react in a meaningful way when there is a "brownout" or gradual loss of power.

One problem with sharply cutting out (like say outputting 0V any time the input voltage is less than 10V, otherwise outputting 8V) would be that it would turn power supply ripple that crosses the 10V boundary into an 8V square wave, abruptly turning downstream devices on and off. This would briefly happen on every power up and shutdown!

[saturated]

Yes sir thanks
One thing that bothers me is wondering if it's just a coincidence that they put these voltage regulators in a TO-220 package is that where the similarities end or is there more to it like maybe internally they are the same as a transistor but lacking a component that a transistor would have

Kinda hard to find info on this

Maybe it's just a big zener diode 

[Kaz Kylheku]

The TO-220 package is probably just chosen for certain heat dissipation: it has a metal tab for screwing to a heat sink and all that. Inside a voltage regulator, there are numerous transistors.  They are all on one piece of silicon. Whether we have a piece of silicion implementing a single TO-220-package transistor or a whole voltage regulator, it doesn't matter to the package.

Packages are deceiving. The ATTiny85 microcontroller is packaged in an 8 pin DIP. It looks exactly like an op-amp. It probably contains on the order of 60,000 transistors.