Question

Q) design and analyze a current limited series voltage regulator that includes op amp and 8V zener diode . The regulated output voltage should be 40V and the output current should be limited to 800mA . The zener current should be 9mA when Vi = 35V.
(solve neatly)

Answer 1

figure below shows the design of the current limited series voltage regulator using op-amp and zener, the zener used is of 8V the op-amp or the transistor T1model not specfically mentioned in design because we can choose opamp such as 741, 351 etc as there are choices and transistor too power transistor like 2N3055 can be opted.

The working of the regulator is simple , let us assume when V_out increases for some reason then V_z increases so that the base current of transistor decreases and its collector current resulting in decrease in V_{out and} vice versa . The design constraints are considered as given V_z=8V, I_z=9mA at V_in=35V , output voltage 40V and I_L=800mA.

please note that the series resistance value is just calculated only for 9mA Zener current and when 35V input design constraint .For higher current to pass through the current limiting resistor must be in ohms.So it has to be designed and selected accordingly