SU421955A1 - DEVICE FOR MEASURING THE HEAT RESISTANCE OF TRANSISTORS - Google Patents

Description

one

The invention relates to the field of electronics and can be used to control the parameters of newer devices.

Devices are known for measuring the thermal resistance of transistors, comprising a heating current pulse generator, a measurement pulse generator, and a source of collector voltage.

However, when using known devices, the accuracy of the measurement of the junction temperature is limited by the accuracy of the pulse measurements of the temperature-dependent parameter — the direct voltage drop across the junction of the transistor; besides, measurements are very laborious.

The purpose of the invention is to increase accuracy and ensure the possibility of automating measurements.

The goal is achieved by the fact that the proposed device contains a regulating null organ, the input of which is connected to a terminal for connecting the base of the tested transistor and to a collector resistor, and the output is connected to a generator of pulses of current.

The drawing shows a block diagram of the proposed device. It contains a heating current generator / pulses, a measuring pulse generator 2, a transistor 3 under test, a collector voltage source 4, terminals 5, 6, 7 for connecting a transistor under test, a collector resistor 8, a zero-control regulator 9, a synchronization circuit 10.

It is known that

Tn - T

th

where is the transition temperature;

traction sensor. (2)

P uj, a,

e UK- trans collector voltage

zistor,

/ K - collector current, st - the duty cycle of the heating pulses. With const

,

, -.

l

The device under test is installed in modes that differ in medium temperature and power dissipated in the transistor, and the same in terms of the transition temperature.

When connecting the test transistor 5 to the terminals 5, 5, 7 at a certain ambient temperature Gr ,, for example

room, through the emitter of the transistor emitter current flows due to the operation of the generators I, 2 and the synchronization circuit 10. Source 4 provides the voltage t / ,; and the power is released on the transistor in accordance with formula (2). During the measuring pulses of the emitter current, the corresponding base current pulses occur, and a signal proportional to them is released on the collector resistor 8. This signal is input to the regulating zero-organ 9. The synchronization signal supplied through the circuit 10 to the regulating zero-organ provides the latter's response only to base current pulses corresponding to the measuring pulses. The control zero-body automatically changes the magnitude of the heating current pulses of the generator 1, and hence the heating power of the tested transistor. The power change is made until the base current pulses during the measurement pulses become zero. At the end of the regulation, t / and the steady-state value / k, calculate the power PI by the formula (2). When the temperature of the medium changes, for example when the transistor is heated in a thermostat, the control process automatically repeats, and a different value of the power P is received.

Then determine the value of thermal resistance of the investigated transistor by the formula

nGer - 7cp2

(four)

The described device is applicable for research only for those transistors, in which the effect of the base current being equal to zero (the phase rotation of the base current) depends on the temperature.

Subject invention

A device for measuring the thermal resistance of transistors, comprising a generator of heating current pulses, a generator of measuring pulses, and a source of collector voltage, characterized in that, in order to improve accuracy and automate measurements, it contains a regulating null organ, whose input is connected to a terminal

Connecting the base of the test transistor and with a collector resistor, and the output is connected to a generator of pulses of heating current.