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which would serve to limit the voltage across the regulator.
If everything so far presented seems obvious enough, let us move to the inversion of this circuit. A negative voltage regulator could just as easily be used. Here the current setting resistor would connect directly to the cathode as would the adjustment pin; the input pin would connect to ground directly or intermediately through a power resistor or zener string as in the previous example. So far we have enjoyed no real advantage to using a negative regulator, other than to confuse many neophytes. But if we connect the input to the regulator directly to the cathode or move the zener diodes in between the cathode and the current setting resistor, we enjoy the advantage of having the metal tab of the TO-220 package and the entire case of the TO-3 package connected to ground. This would make the regulator safer to handle while it was in use and would eliminate the need for isolation washers to separate the regulator from its heat sink; in fact, the chassis could be used directly as a heat sink. n
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