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Diodes and Rectifier Circuits

Diodes are semiconductor devices that allow current to flow in only one direction.[*] Diodes are composed of a junction between a P-type semiconductor and an N-type semiconductor. Most diodes are made of silicon. Silicon diodes turn-on strongly when the p-side is made approximately 0.7V higher than the n-side. The expression relating current through a diode to the voltage applied across a diode is given by:  
 \begin{displaymath}
I_d = I_S\left (exp \frac{V_d}{V_t}-1\right )\end{displaymath} (1)
where Id is the diode current. Vd is the voltage from the p-side to the n-side. Vt is called the thermal voltage which comes from basic physics and is equal to 0.026V at room temperature. IS is the saturation current which depends on the way the diode is fabricated. IS can be obtained from data books from specific diode manufacturers. From equation (1.1), it is clear that when $V_d \gg V_t$,a large current can flow. However, when Vd < 0 a negligibly small reverse saturation current will flow.

Diodes have many electronic applications. In this lab we will demonstrate that the diode is a rectifier, and then show how a rectifier can be used with a transformer to construct a DC power supply from AC wall current. You will then use the power supply you make to power op-amp circuits.


 
  • ENEE306 Lab1 Electronics for Audio and Comm unications
    next up previous contents
    Next: Experiment: Simple Half-Wave Rectifier: Up: Laboratory 1: Diodes and Previous: introduction
    Neil Goldsman
    10/23/1998