Module 1 Semiconductor (pnJunction) Diodes（模块1半导体pn结二极管）.pdf

Module 1 Semiconductor (pn-Junction) Diodes What are they and what is their purpose? Diodes are electronic check valves which allow current to flow freely in one direction, but block current flow in the opposite direction. Open Essentially, they serve the same function in circuits, as the valves in your heart and veins do in your body. Closed How do they work? (Module 2) 2 Semiconductor (pn-Junction) Diodes Physically, diodes are formed by the interface between two regions of oppositely doped semiconductor (i.e., pn junction) and are thus, structurally, the simplest semiconductor devices used in electronics. Circuit Symbol: Ideal Diode An ideal diode is a two-terminal device defined by the following non-linear (current- voltage) iv-characteristic: “open-circuit” “short-circuit” Note: From the above, it follows that zero power dissipation occurs in an ideal diode! 3 Forward Biased Regime (v 0): Zero voltage drop occurs across a forward-biased ideal diode (i.e., the diode behaves like an ideal short circuit). Reverse Bias Regime (v 0): Zero current flows in a reverse-biased ideal diode (i.e., the diode behaves like an open circuit). Determine the polarity of the voltage across the diode, then “replace” the diode with its equivalent circuit (either open-cct. or short cct.) and proceed with linear circuit analysis. DC Behavior: e.g. The diodes in each of the follo