Just a quick reply and some old school info: when 79xx ( the negative version ) regs are not loaded sufficiently they will exhibit strange behaviour. If you want the device to be reliable just load the negative reg with a resistor in series with a "power-on" LED to make sure enough current is drawn from the reg for it to function correctly.
jean-paul said:Just a quick reply and some old school info: when 79xx ( the negative version ) regs are not loaded sufficiently they will exhibit strange behaviour. If you want the device to be reliable just load the negative reg with a resistor in series with a "power-on" LED to make sure enough current is drawn from the reg for it to function correctly.
Good idea,it wouldn't hurt to put one on each regulator,just to provide a bit of a minimum load.
DigitalJunkie said:
Good idea,it wouldn't hurt to put one on each regulator,just to provide a bit of a minimum load.
Actually, you need to put it on the - side only. It's a start-up problem with the negative reg if the current is drawn directly from + to -. Having a bit of extra current to gnd on the - side insures that it starts up normally.
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