Electronics > Beginners

UA7812 & TIP147 current booster

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GreyArea:
Hi, I've been trying to create the attached circuit on my breadboard with little luck, been staring at it for literally hours - I'm sure I have it wired correctly (heard that before?) but it's not working as I expect.

I have 15v input connected across 1) & 2) on the schematic, across the output 3) & 2) I'm measuring 14v, instead of the expected regulated 12v.  After a few seconds the 7812 gets extremely hot, even with no load.  Set at 15v, my PSU reports 250mA current draw with no load apart from the circuit drawn.

I don't actually have any .33uF capacitors so I'm using .1uF across the 7812 input and outputs.

What is the most likely cause for the above behaviour do you think?  Thanks.

HB9EVI:
why do you take a darlington transistor (TIP147)? The schematic says nothing about that

T3sl4co1l:
If you've wired it correctly, as shown, and the capacitors aren't burned out, then the regulator probably is.

Tim

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