I. The purpose of the experiment
1. Measure the relationship between forward and reverse volt-ampere characteristics of diodes.
2. Learn and understand the basic working principles of rectifier and filter circuit.
3. Master the basic characteristics of AC circuit and the measurement method of AC parameters.
Two. experimental installation
DC power supply to be tested, sliding rheostat, unipolar switch, voltmeter, ammeter, microammeter and diode.
Three. Experimental principle
According to the conduction principle of PN junction, the diode is in conduction only under the condition of positive bias, and its volt-ampere characteristic curve is shown in the following figure:
(1) positive property
Refers to the diode characteristics when the forward bias is applied, that is, the applied voltage V >；; 0
When 0
Where Io can be replaced by the measured reverse current Is, v is the applied voltage, t is the thermodynamic temperature, e is the number of electrons (1.6022 *10-19c), and k is the Boltzmann constant.
The dead-time voltage vth of silicon diode is about 0.6V, and the dead-time voltage vth of germanium diode is about 0.2V. ..
(2) Reverse features
Refers to the diode characteristics when the reverse bias voltage is applied, that is, the applied voltage V.
When VBR
When V & gt=VBR, the reverse current increases sharply, and VBR is called reverse breakdown voltage.
Four. experimental procedure
(1) Connect the light bulb according to the external connection mode in Figure (b), and switch the light bulb to the diode forward connection mode. Starting from 0.6V, measure every 0.02V until the current is large (at this time, the voltage on the diode is about 0.8V), and draw the forward volt-ampere characteristic curve of the diode.
(2) Connect the wiring according to the interconnection method in Figure (a), which will be changed to diode and reversed. The measuring voltage is 0 ~ 5.0 V. Measure the current value every 0.5V to find out the reverse volt-ampere characteristics of the diode.
(3) Measuring Boltzmann constant
The volt-ampere characteristic curve of diode can be expressed as
Where Io can be replaced by the measured reverse current, V is the applied voltage, T is the thermodynamic temperature, E is the number of electrons (1.6022 *10-19c), and K is the Boltzmann constant. Find k by formula.