
148
'a) (b)
Fig. 9.15 Construction of a small-signal silicon junction diode, (a) spring-contact, (b)
'whiskerless'
rectification, can be made use of in voltage-varied capacitors, or
varactors. The capacitance of a diode, being dependent on the
thickness of the depletion layer, and that thickness varying with the
reverse voltage, as shown by comparing Fig. 9.11 with 9.10, the
capacitance must vary with reverse voltage. Since increasing the
voltage increases the thickness of the depletion layer, it reduces the
capacitance (Sec. 3.3). This property has uses such as tuning
receivers (Sec. 21.6).
One quite essential thing we have been taking fo