Which of the following devices has characteristics very close to the ideal voltage source?

Explanation:

The device used for the voltage regulator and also gives characteristics that are very close to that of an ideal voltage source is a Zener diode.

It is used to regulate the voltage level. It generates a fixed output voltage that remains constant for any changes in load conditions or input voltage.

Zener diode:

• It is a PN junction (silicon PN junction) diode and has a low specified reverse voltage which takes advantage of any reverse voltage applied to it.
• From the I-V characteristics curve above, the voltage across the diode in the breakdown is almost constant.
• In the breakdown region, it is used in voltage regulator applications.