Question

Which among the below mentioned parameters of transistors is/are likely to get affected or exhibit/s variations due to an increase in temperature?

(a) Base-to-Emitter voltage (VBE)

(b) Current Gain (βdc)

(c) Base-to-Emitter voltage & Current Gain

(d) Forward resistance

I had been asked this question during an internship interview.

My question is taken from Thermistor and Sensistor Compensation topic in chapter Transistor Biasing and Thermal Stabilization of Electronic Devices & Circuits

Answer 1

The correct choice is (c) Base-to-Emitter voltage & Current Gain

Explanation: In a transistor, the junction temperature mainly depends on the quantity of current passing through it. As the temperature increases, various parameters of transistors exhibit variations. These parameters include; base-to-emitter voltage (VBE), current gain (βdc) & reverse saturation current (IICBO).

Due to an increase in temperature, base-to-emitter voltage (VBE) decreases and eventually tends to change the Q-point. Since the current gain is a function of collector current (Ic), variation in current gain also ultimately varies collector current.