5V Low Drop Out Regulator Low Volt by BD438
The general regulator circuit, need input voltage is higher than the
output voltage. So cannot apply to the input voltage is higher just
little than the need voltage. But this circuit you can have the five
volt output from input voltage only six volt of the normal battery.
As circuit picture below. The load is connected with collector pin of
the transistor output. Connection this way makes transistor works in a
saturation. As a result the voltage drop across the collector pin and
emitter pin very low (because to be the saturation voltage).
-And this current depends on a type of transistors, Which is set about
0.5 amperes, has a voltage drop is 0.2 volts. But for all circuit need
plus with voltage across R6. (Current limiting resistor)
At voltage across R6 is about 0.5 volts. T3 is activated and the output
current is limited there. LED-D1 is the second function is indicate
working and the reference voltage. Which is set 1.5 volts to 1.6 volts
at emitter pin of T1, for base current to drive it works.
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