There will be a small voltage across the diode, about 0.6 volts for
Si, and this voltage will be largely independent of the current,
very different from a resistor.
What is a Reverse Biased Diode?
If the polarity of the applied voltage is reversed, then the diode
reverse biased and will appear non-conducting. Almost no
current will flow and there will be a large voltage across the
Fig - 2 : Reverse Biased
The non-symmetric behavior is due to the detailed properties of the
pn-junction. The diode acts like a one-way valve for current and
this is a very useful characteristic. One application is to convert
alternating current (AC), which changes polarity periodically, into
direct current (DC), which always has the same polarity.
household power is AC while batteries provide DC, and converting
from AC to DC is called rectification. Diodes are used so commonly
for this purpose that they are sometimes called rectifiers, although
there are other types of rectifying devices.
Figure 3 shows the input and
output current for a simple half-wave rectifier. The circuits gets
its name from the fact that the output is just the positive half of
the input waveform.
A full-wave rectifier circuit (Figure 4)
uses four diodes arranged so that both polarities of the input
waveform can be used at the output. The full-wave circuit is more
efficient than the half-wave one.
Fig - 3 :
Fig - 4 : Full-Wave Rectifier