Laboratory work: studying the current–voltage characteristic of a semiconductor diode
The aim is to study the dependence I(U) of a diode. Equipment: a diode, a low-voltage DC source (a safe value set by the teacher, usually not above 6–12 V), a milliammeter, a voltmeter, a rheostat connected as a potentiometer, a protective resistor (to limit the current in forward bias), a switch, wires. Procedure: 1) assemble the circuit and show it to the teacher; 2) set the rheostat slider to U = 0; 3) close the switch and raise the voltage in steps of 0.1 V, noting U and I each time; in forward bias the current must not exceed the value in the diode’s datasheet; 4) swap the source terminals (diode reversed) and measure U and I, never exceeding the datasheet’s maximum reverse voltage; 5) plot the graph for both directions. Result: in the forward direction the graph is not linear – for silicon the current rises sharply above ≈ 0.6–0.7 V; in the reverse direction the current is very small (a few μA) because only minority carriers pass.
Only under the teacher’s supervision and at low voltage: carry out the work; never exceed the datasheet reverse voltage; never apply forward voltage without the protective resistor. Do not use a 36–42 V supply; follow the school’s safety rules.