Resistor Color Coding

Basic Concepts about Transformer

A transformer transfers alternating voltage at one circuit to another circuit without a change in power and frequency. Fig. 1 shows the general configuration. The iron core is made up of laminated thin sheets of silicon steel. Each sheet is 0.35 mm thick insulated on both side by a thin layer of varnish or paper.

  
Here there is two coil. The primary coil has N₁ turns and connected to the source of ac supply. The secondary coil has N₂ turns and supplies power to the load.

PN - Junction Diode

The simplest semiconductor device has two regions, one region doped with p-type impurity and the second region doped with n-type impurity. The impurity concentration changes from donor to acceptor at the boundary. The dopants are assumed to be shallow, so that the electron (holes) density in the n-type (p-type) region is approximately equal to the donor (acceptor) density.

	Figure: (01)  Cross-section of a p-n junction

We will assume, unless stated otherwise, that the doped regions are uniformly doped and that the transition between the two regions is abrupt. 

Figure: (02)  Depletion Layer of a p-n junction

Figure:(03) PN-Junction Diode V-I Characteristic

           Figure: (04) Ideal PN Junction Diode V-I Characteristic