Solid State Music V1B question

Tony Duell ard at
Fri Jul 15 19:25:36 CDT 2005

> The 1N4742 is a 1w part which at 12 volts is well within the amperage
> ratings of a 7812.

Come again? The 7812 is a 1A output regulator. So the load current can 
vary between 0 and 1A. If you replace it with a resistor + zener circuit, 
the zener current would haev to be around 1A when the load current was 
essentially zero. That means the poor old zener is dissipating 12W

Now I don't believe for an instant that the character generator chip 
draws anything like 1A, so you could make do with a larger resistor and 
thus less power dissipated in the zener. 


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