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|_O_| <-- tab is connected to center pin
|   |
|___| TO-220 Pin Diagram
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 123

Adjustable regulators

LM317
1: adjust
2: output
3: input
tab: output

LM338/LM138 (5 amp positive regulator, 12a peak)
1: adjust
2: output
3: input
tab: output
1.2-32v output differential above input voltage.
V[ref]=1.25v
V[in]=delta 40v
V[in]=V[out] + 40v

LM137/LM337 adjustable negative regulator (1.5a)
1: adjust
2: input (power supply side)
3: output (application side)
tab: input
V[out]=delta -40v input
V[ref] = -1.25v
-V[out] = -1.25v * ( 1 + R2/R1 ) + ( -I[adj] * R2)
-I[adj] is small and usually ignored.

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LM78XX/LM79XX fixed regulators 1.5 amp with heat sink
V[in]=35v, V[out]=XX

LM78XX
1: input
2: ground (adjust)
3: output
tab: ground (adjust)

LM79XX
1: ground (adjust)
2: input (power supply side)
3: output (application side)
4: input

LM79XX adjustable:
V[out] = V[ref] * ( (R1 + R2) / R2 )