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

Optoelectronic, Need a project in Optoelectronic with simulation in Optispi...

Need a project in Optoelectronic with simulation in Optispice or Matlab.with complete report and presentation. ANy ideat about project and how much does it cost.

Discuss the control words of ic8259, Discuss the control words (ICWS) of IC...

Discuss the control words (ICWS) of IC8259. The Intel 8259 is a single chip programmable interrupt controller. It is compatible with 8086, 8088 and 8085 microprocessor. It is a

Microcontroller programing, assembly language program for finding largest ...

assembly language program for finding largest number from a given array of 8 bit numbers

Find the t-domain forced response in glc parallel circuit, Consider a GLC p...

Consider a GLC parallel circuit excited by i(t) = Ie st in the time domain. Assume no initial inductive current or capacitive voltage at t = 0. Draw the transformed network in the

Shunt dc motor, Shunt DC motor In this arrangement, the armature and f...

Shunt DC motor In this arrangement, the armature and field coils are connected in parallel (the motor is called 'shunt connected').     Analysis With refere

What is basic working of mosfet, Q. What is basic working of MOSFET? Th...

Q. What is basic working of MOSFET? The metal-oxide-semiconductor construction leads to the name MOSFET, which is also known as insulated-gate FET or IGFET. One type of constru

Speech Timer, Speech timer where max time is 5 minutes Use the switche...

Speech timer where max time is 5 minutes Use the switches for: start switch reset switch use the lights to represent: the “green” light meaning the

Diode, #quetunnel diode stion..

#quetunnel diode stion..

Relative permeability, The force between two wires 1 metre apart and each c...

The force between two wires 1 metre apart and each carrying 1 amp is 2 x 10 -7 Newtons when in a vacuum (or in practice, air).However, it is found experimentally that the force is

Describe the two core-excited states, Using the optimized 6-311G(d,p) geome...

Using the optimized 6-311G(d,p) geometry determined in question 1, perform the following equivalent core calculations for any two inequivalent carbons of butadiene: (a) Equivale

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