sentences:  In silicon diodes up to about 5.6 volts, the Zener effect is the predominant effect and shows a marked negative temperature coefficient.Above 5.6 volts, the avalanche effect becomes predominant and exhibits a positive temperature coefficient.In a 5.6 V diode, the two effects occur together, and their temperature coefficients nearly cancel each other out, thus the 5.6 V diode is useful in temperature-critical applications.