The rectifying action of a junction between p-type and n-type semiconductors is of universal untility in integrated cricuits. The insulating property of a reverse-biased junction is the means by which components are isolated from one another. The prime aim of this page is to derive an equation to describe the I-V characteristi of a p-n junction. It will also explore briefly four other applications: the varactor diode (avoltage-controlled variable capacitor), the light-emitting diode, the photodiode and the schottky diode.
In addition to deriving the current-voltage characteristic, we will also present another frequently-used type of model for an electronic device: the small-signal equivalent circuit. This represents the behaviour of the device when a small alternating voltage is applied to the terminals. Since the current and voltage in a diode are not proportional to one another (we say that the I-V relation is non-linear , then V/I and delta V/I cannot be equal to one another, and the small-signal resistance - which is a component of the equivalent circuit _ has to be caluculated from the equation relating I and V. But first we must consider the potential disctribution within a p-n junction having no bias voltage applied across it.
We need to consider the link between:
diffusion current
charge transfer
potential difference
electric field
drift current
Here are a few useful equations:
Jn = neueE + De
e dn/dx=0
Jp = peueE - Dhe dp/dx
=0
To find out more, please click the following pages:
page 1
page 2
page 3
games
Here is a question to test your understanding of the above paragraph:
question:
What is 1 + 1 =?
If you think you've learnt something through reading this page, please sign my guess book.