I'm curious about a little something. Why do positive voltage regulators (like 7815) have their case connected to GND and negative ones (7915) have it connected to Input voltage (Vin)? Seems to me it would be more logical and practical if both had it grounded. Can someone enlighten me on the reason for this? TIA
Question about 78xx AND 79xx regulators in TO-220 cases
Nov 20, 2004
2 Replies
The silicon chip is soldered to the can for best heat transfer, and in most linear IC processes the silicon substrate has to be the most negative potential to allow using back-biased junctions for isolation.
There are a few exceptions, like LM317s I think.
John
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