# LM337 negative voltage regulator gets very hot, is this normal? [duplicate]

I used the LM337 negative regulator to regulate a +12V from a PC power supply. And connected the GND to input and the +12 to ground of the circuit, and i got it work (i mean it's regulating the voltage) but the problem is it's get very hot even with heat sink connected to it. Is that normal because i didn't keep it on for a long time.
It used to regulate 12 volts to 3.2 volts.

## marked as duplicate by m.Alin, PeterJ, Majenko, Dave Tweed♦Jun 18 '14 at 11:36

• How much current? – Ignacio Vazquez-Abrams Jun 18 '14 at 5:16
• 700 mA that used to derive a RGB LED. – user45798 Jun 18 '14 at 5:18
• LM337 is a linear regulator, so (12V - 3.2V) * 0.7A = 6 watts of power must be dissapated. Did you use heat sink grease for thermal connection between LM337 and its heatsink? (I assume TO-220 package) If heat sink is just bolted to LM337 there is not always enough thermal contact. – MarkU Jun 18 '14 at 5:33
• Thank you for answers. So it is normal to get that much of heat ? – user45798 Jun 18 '14 at 5:54
• You'll need to do the thermal calculations to be certain, but 6W will generate a fair amount of heat regardless. – Ignacio Vazquez-Abrams Jun 18 '14 at 6:12

$(12\text{V} − 3.2\text{V}) ⋅ 700\text{mA} = 6.16 \text{W}$