Mumbai University > Information Technology > Sem3 > Analog and Digital Circuits

Marks: 4M

Year: Dec13

• Voltage regulators are used to achieve constant output voltage.

• Voltage across the Zener diode remains constant equal to Vz (Zener breakdown voltage) when it is reverse biased and operated in zener region of the reverse characteristics.

• This characteristic of zener diode is used for voltage regulation.

• Following diagram 1.2 shows the regulator circuit using Zener diode.

• $V_{in}$ is the unregulated input dc voltage, RC is the resistor used for current limiting and $R_L$ is the load resistor.

• Since Zener diode is shunted across the load resistor it is called as Zener Shunt Regulator.

• The input voltage should always be higher than the breakdown voltage.

• When $V_{in} \gt V_Z$ and$ I_{Z(MIN)} \lt I_z \lt I_{Z(MAX)}$ constant voltage is obtained across the zener diode equal to the breakdown voltage $V_Z$ which is the regulated output voltage.

• Refer to chap 1 question 1 for Zener shunt regulator.

• The change in the load voltage due to the change in input voltage (line voltage) is expressed in terms of a factor called line regulation or the voltage stability factor ($S_V$).

  $S_V=∆V_o /∆V_{in}$