Voltage regulator
with zener diode parallel to the load.

Voltage regulator with zener diode parallel to the load are generally used when is necessary to obtain a reduced voltage of moderate power from the main supply line.

Since it is an analog regulation it has the property to give a stable voltage, without parasitic fluctuation and with limited noise levels. The very low energetic efficiency makes it useful mainly when small current are required.

Data input

Max supply voltage . . . V_MAX

V

Min supply voltage . . . V_MIN

V

Stabilized voltage required . . . V_Z

V

Maximum required current . . . I_OUT

mA A

Results.

Dropping resistance . . . R

Ohm

Maximum power dissipated by resistor . . . W_R

W

Maximum power dissipated by zener . . . W_Z

W

Maximum voltage drop . . . V_R MAX

V

Minimum voltage drop . . . V_R MIN

V

Max power dissipated by resistor W_R.
It refers to the condition in which supply voltage is at the maximum value (V_MAX), the magnitude of the load is indifferent.

Max power dissipated by zener diode W_Z.
It refers to the condition in which fails the load and the supply voltage is at the maximum value (V_MAX).

Power of the zener.
The zener diode to be installed should be selected with a power at least equal to W_Z.

Zener temperature coefficient.
As temperature increases, at same current flowing through the zener, the zener voltage increases if V_Z > 5V and it decreases if V_Z < 5V. So the temperature coefficient can, be negative or positive.
A diode with a V_Z near 5V has a reduced temperature coefficient.