Electrical Circuits and Electronics课件（华南理工）Lecture 26.pptVIP

Electrical Circuits and Electronics School of Electric Power Electrical Circuits and Electronics School of Electric Power Electrical Circuits and Electronics School of Electric Power Electrical Circuits and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Electrical Circuit and Electronics School of Electric Power Chapter 8 Diodes Aim Understand diode operation and select diodes for various applications; Use the ideal-diode model and piecewise-linear models to solve circuits; Understand various rectifiers and wave-shaping circuits. Lecture 26 Basic Diode Concepts and Diode Model Diode Symbol The diode is a basic but very important device that has two terminals, the anode and the cathode. Anode Cathode + - Physical Structure The diodes consist of a junction between two types if semi-conducting material; n-type material: impurities with large numbers of electrons moving freely; p-type material: impurities are employed to create positive charged particles (holes). Holes Free electrons Electric field barrier Anode Cathode Forward Bias and Reverse Bias Forward bias: voltage applied to the diode is positive, relatively large amounts of current flow for small voltages. Reverse-bias region: moderate negative value of , the current is very small in magnitude. Forward-bias region Reverse-bias region Anode Cathode + - Reverse-breakdown Region Sufficiently large reverse-bias voltage is applied to the diode, operation enters the reverse-breakdown region of the characteristic, and currents of large magnitude flow. Reverse-breakdown region Anode Cathode + - Zener D