I have created this simulation ( see below) of a transistor and zener diode voltage regulator. The output is supposed to be a steady 5 V. But it is like the top bit s cut, to an approx 4.4 V value, then it plunges to the minimum voltage value. I really dont understand why and how to fix it
The simulation has an AC source feeding the Zener Diode - Series pass transistor circuit. Replacing the AC source with the DC source should eliminate voltage plung situation. Alternatively inserting a rectification circuit between AC source and the Zener regulation circuit will also solve this issue.
The 4.4V output voltage situation can be solved by selecting a 5.6V Zener diode such as a 1N4734A from Vishay
Below is a example zener diode - series pass transistor 5V output circuit
Below is a list of parts from other vendors
Alternatively below is list of 1N47 series zener diodes from Vishay