<WORK 02>

Thermal dependence of forward characteristics of semiconductor devices

Input tasks

Measure the forward diode characteristic by “TESTER OF DIODES” and digital storage oscilloscope.
The measurement can be provided for maximum pulse forward current IF = 2000 A.
Plot the dependence between temperature and UT0 in the first graph, plot the dependence between temperature and differential resistance rT in the second graph. At last count and make graph with the dependence P_FAV = f (t).
The temperature range is from 25°C up to 120 °C.

Circuit's diagram

Front panel of "TESTER DIOD"
1,2-outlets of measured component, 3-peak-voltage indicator (UF), 4-pernament forward current, 5-fine control of current IF; 6-START push-button, 7-coarse control of current IF, 8-main switch, 9-sensing output of current I_F, 10-externall triggering of oscilloscope

Measured components

1.	MDD 431 - 80	2.	MTT 431 - 80
3.	MDD 431 - 63	4.	MTT 442 -125
5.	MDD 442 - 125

Parameters of measured devices are available in this catalogue.

Process of measurement

Measurement will be provide during the temperature increases. Turn-on "TESTER DIOD", thermostatic regulation and oscilloscope. (if they are not turn-on) Open the cover of the thermostatic platform and connect measured component, close the cover.
Check and record the value of actual temperature. Set approximately U_C = 200 V using knob 7 (coarse) and 5 (fine). Digital oscilloscope should be switched into XY mode, scaling is both on axe X and Y 0,5 V/degree. If the measured component is thyristor (SCR), it is necessary to provide latch-up (turn-on). For this purpose, device "TESTER OF DIODES" is equipped with a permanent source of DC current. Using this source it is possible to turn-on measured thyristor (generate latch-up). Push START button a check the achieved value of pulse current. When not sufficient, add some voltage on the control knob (7 and 5). When repeating this procedure, it is necessary to repeat turning-on the thyristor. Save figure from oscilloscope in to file (BMP or TIFF).
Switch oscilloscope into time-domain mode with triggering NORMAL. Trigger level should be synchronized with channel Y and low. Scaling is 5 ms/degree, starting point of waveform lies in the left part of the display. Scanning can be started pushing RUN in the trigger menu and stopped pushing STOP bottom. Save data into CSV file and check on PC.
Open the cover and connect another component to repeat this procedure. After measuring all available components, change temperature using step approximately 20°C. The next figure explains how to determine UTO and rT.

For calculating the value of PFAV use following equation. Value of I_FAV is available in catalogues.

Typical measured waveforms

Waveform 1: current (scanned from resistor 1mOhm), waveform 2: voltage (probe 1:1).

Waveform of volt-ampere characteristic in XY mode.