Electrical energy is transmitted to homes as alternating current (a.c.), but many everyday electronic gadgets, like smartphones, require direct current (d.c.) to operate. A semiconductor diode is a two-terminal electronic component that allows current to flow in one direction only. This unique property makes it essential for rectification—the process of converting alternating current into direct current.
See how forward and reverse bias change the depletion layer, and how half-wave, full-wave and capacitor-smoothed outputs appear on a CRO.
A semiconductor diode is formed by joining a p-type semiconductor and an n-type semiconductor, creating a p-n junction. The triangle in the circuit symbol represents the anode (+), while the vertical bar represents the cathode (−).
Positive terminal of the cell is connected to the anode (p-type) and negative terminal to the cathode (n-type). The depletion layer becomes thinner, junction voltage decreases, resistance becomes very small, and current flows.
Positive terminal is connected to the cathode (n-type) and negative terminal to the anode (p-type). The depletion layer becomes thicker, junction voltage increases until it reaches the battery potential difference, resistance becomes very high, and current stops.
Rectification is the process of converting alternating current into direct current. A single diode gives half-wave rectification, while four diodes in a bridge arrangement give full-wave rectification.
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What happens to the depletion layer and the diode resistance when a diode is connected in reverse bias?
In a bridge rectifier, which diodes conduct during the positive half cycle, and which conduct during the negative half cycle?
How should a capacitor be connected relative to the load resistor to smooth out rectified current?
Diodes convert a.c. into d.c. by changing the shape of the voltage wave magically.
Diodes simply conduct in one direction and block current in the reverse direction. By routing paths using one or four diodes, alternating current is forced into a unidirectional (rectified) flow.
A capacitor generates electrical energy to smooth the output current.
A capacitor only stores electrical energy when the output voltage rises (charges) and releases that stored energy when the voltage drops (discharges), preventing output current from reaching zero.
Objective: Identify diode biasing, rectification and capacitor smoothing.
1 What happens to a p-n junction diode when it is connected in forward bias?
2 What is the function of a capacitor connected in parallel to a load resistor in a rectification circuit?
3 The process of converting an alternating current into a direct current using semiconductor diodes is known as .
4 In a full-wave bridge rectifier, the arrangement uses semiconductor diodes to allow current to flow through the load in the same direction during both half cycles.
Drag each term to the correct meaning. If using a phone, tap the answer first, then tap the matching box.
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