What is thermal runaway, Electrical Engineering

Assignment Help:

Q. What is thermal runaway? State one method to prevent the same?

The effect of changes in leakage current (ICO)  and current gain(b) on the dc bias point is given by the equation

IC = bIB + (1+b) ICO.

The collector current increases with the increase in temperature since b increases with increase in temperature.

           ICO doubles in value for every 100 C increase in temperature.

This leads to increased power dissipation with further increase in temperature. Being a cumulative process it can lead to thermal runaway resulting in burn-out of the transistor. The self-destruction of an unstabilized transistor is called thermal runaway. However, if by some technique, IB is made to fall with increase in temperature automatically, then decrease in the term bIB can be made to neutralize the increase in the term (1+b)ICO, thereby keeping IC almost constant. This will achieve thermal stability resulting in bias stability.

Stabilization technique makes use of a resistive biasing circuit that permits such a variation of base current (biasing current) IB as to maintain the collector current IC almost constant in spite of variations in reverse saturation current ICO and b.

DT = Tj - TA = θPD

where, PD = power in watts dissipated at the collector junction

TA = ambient temperature

Tj = junction temperature

θ = constant of proportionality called thermal resistance


Related Discussions:- What is thermal runaway

Working of equalizer circuit, Q. Working of Equalizer circuit? Equalize...

Q. Working of Equalizer circuit? Equalizer circuit: Equalizers are combination of passive components (capacitors, resistors and so on) that are used to regulate the amplitude a

Newton raphson , hi can you help with newton raphson?

hi can you help with newton raphson?

Controls and system, transfer function of Lube Oil Cooler Temperature

transfer function of Lube Oil Cooler Temperature

Find the magnitude of the force, Q. A solenoid of cylindrical geometry is s...

Q. A solenoid of cylindrical geometry is shown in Figure. (a) If the exciting coil carries a steady direct current I, derive an expression for the force on the plunger. (b) F

Analog circuit, What is the disadvantages of diodes as a series element in ...

What is the disadvantages of diodes as a series element in a clipper?

Digital control system, block diagram of digital control system and explain...

block diagram of digital control system and explain each block

[email protected], a sensorless brushless DC motor control with back emf ...

a sensorless brushless DC motor control with back emf (zero crossing point ) technique, using Arduino Microcontroller board control and describe in C. program language.

Determine the voltages, Question: a) For the circuit shown in figure ...

Question: a) For the circuit shown in figure (i) Determine the voltages across R1 and R2 and (ii) Determine the current which flows across R1 and R2. Both D1 and D2 a

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd