What is thermal runaway, Electrical Engineering

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

Posted Date: 6/11/2013 5:16:51 AM | Location : United States

Related Discussions:- What is thermal runaway, Assignment Help, Ask Question on What is thermal runaway, Get Answer, Expert's Help, What is thermal runaway Discussions

Write discussion on What is thermal runaway
Your posts are moderated
Related Questions
Calculate the approximate donor binding energy Calculate the approximate donor binding energy for Si (r = 11.7,m x n = 1.18 m 0 ) Solution: From E= m * n q 4 / 2(4 πε 0

1.)  A three phase, D0 HP, 1765 rpm, BA0 V induction motor operating at three quarter load has an efficiency of 91% and a power factor of 87%. Determine active power, apparent pow

Q. The 50-turn coil in the configuration of Figure is rotated at a constant speed of 300 r/min. The axis of rotation is perpendicular to a uniform magnetic flux density of 0.1 T. T

(a) contains a freewheeling diode Dm, commonly connected across an inductive load to provide a path for the current in the inductive load when the switch S is opened after time t (

Q. A charge variation with time is given in Figure. Draw the corresponding current variation with time.

Sing Flag If D7  ( bit left  most bit)  of accumulator  (which  some  exceptions) is 1 as a result  of any  arithmetical  or logical operations sign flag  is set ( bit  corresp

design a excess3 to bcd code converter using only nand gates

An interrupt which can be never be turned off (ie. disabled) is called as Non-Maskable interrupt.

i av designed my circuit in proteus and written the java graphical code for analysis of the results....i need help on how i can run this circuit in proteus and get the results in t