terminal is connected to the anode (Fig. 19-4A). No current will flow if the battery is re-versed (Fig. 19-4B). The resistor is included in the circuit to prevent destruction of thediode by excessive current.It takes a certain minimum voltage for conduction to occur. This is called the for-ward breaker voltage of the junction. Depending on the type of material, it varies fromabout 0.3 V to 1 V. If the voltage across the junction is not at least as great as the for-ward breaker value, the diode will not conduct. This effect can be of use in amplitudelimiters, waveform clippers, and threshold detectors.You’ll learn about the various ways diodes are used in the next chapter.How the junction worksWhen the N-type material is negative with respect to the P-type, as in Fig. 19-4A, electrons flow easily from N to P. The N-type semiconductor, which already has an ex-cess of electrons, gets even more; the P-type semiconductor, with a shortage of 364 Introduction to semiconductors19-2Pictorial representation of hole flow. Small dots represent electrons,moving one way; open circles represent holes, moving the other way.19-3Schematic symbol for asemiconductor diode.