Band-Gap Voltage Reference

It is generally known that the accuracy of measurements in electronic circuits is mainly a function of the stability and reliability of the reference against which the unknown quantity is compared. There- fore, everything feasible should be done to maintain the stability of the reference, i.e., counteract 1 the adverse effects of variations in the ambient temperature, supply voltage, and load cur- rent. The zenerdiode in Fig. 1 is a usable reference device for applications where the above three parameters are not sub- ject to appreciable variation. The "super zener" in Fig. 2 features excellent stability and 2 Ub is hardly affected by variations in the supply voltage and the load current. Although the tem- perature coefficient of the super zener circuit can be optimized by careful dimen- sioning of the components, there exists a still better way for making a precision voltage ref- erence. The term band gap refers to the difference between two dis- crete energies of the outer four ...