Version 4
SHEET 1 1392 680
WIRE 112 112 -16 112
WIRE -16 144 -16 112
WIRE 112 144 112 112
WIRE 112 256 112 224
WIRE 224 256 112 256
WIRE 112 272 112 256
WIRE 224 288 224 256
WIRE 112 400 112 336
WIRE 224 400 224 368
FLAG -16 224 0
FLAG 112 400 0
FLAG 224 400 0
SYMBOL zener 128 336 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D1
SYMATTR Value 1N750
SYMBOL res 96 128 R0
SYMATTR InstName R1
SYMATTR Value 242
SYMBOL voltage -16 128 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 208 272 R0
SYMATTR InstName R2
SYMATTR Value 470
TEXT 160 -32 Left 4 ;Raw voltage regulator with zener diode.
TEXT 352 136 Left 2 ;The zener diode regulates the voltage by working in the breakdown region.\nR1 limits the current from the source.\n \nSizing: the load voltage is the nominal zener voltage 4.7V.\nThen IR_2 = 4.7/R2\n \nFrom the datasheet the zener current is found. R1 must be equal to:\n \nR1 = (V1 - Vz)/(Iz + IR_2) = (12 - 4.7)/(20mA + 10mA)
TEXT -48 424 Left 2 !.tran 1