Q11 Describe how a temperaturecompensated zener diode is for

Q11: Describe how a temperature-compensated zener diode is formed.

Solution

Zener diode by connecting the Zener diode in series with forward-biased diodes having a temperature coeflicient opposite to that of the Zener diode. The forward-biased diodes and the Zener diode are then packaged as a single unit so that the temperature dependency of the Zener diode is balanced by the forward-biased diodes. Thus, the positive temperature coefiicient of the Zener diode would be cancelled by the negative temperature coeflicient of the forward-biased diode, a sufficient number of forward-biased diodes being chosen to provide a negative temperature coefiicient equal to the positive coefficient of the Zener diode. Ideally, a situation that rarely exists, as will be explained more fully hereinafter, the temperature coefiicient of the package Will equal zero. Unfortunately, the ideal situation rarely obtains, and it thus becomes necessary to segregate the constructed temperature compensated Zener diodes according to their respective temperature coefficient ; those approaching the temperature coefficient of zero representing a very small fraction of the total number of devices processed.