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

What is dual tone multi frequency, Q What is Dual Tone Multi Frequency? ...

Q What is Dual Tone Multi Frequency? Dual Tone Multi Frequency (DTMF) was first introduced in 1963 with 10 buttons in Western Electric 1500 -type telephones. DTMF was originall

Digital electronics, With the use of clocked JK flip-flops, draw and explai...

With the use of clocked JK flip-flops, draw and explain the working principle of a 3-bit binary ripple counter.

State the functions of a fuse, State the functions of a fuse. Fuse is ...

State the functions of a fuse. Fuse is a protective device that made of a thin wire or strip. This strip or wire is placed with the circuit this has to protect, therefore the

Give a brief description of differentiating circuits, Q. Give a brief descr...

Q. Give a brief description of differentiating circuits ?                Differentiation is a measure of the rate of change. A differentiating circuit produces an output voltag

Bonding forces and energy bands in solids, Bonding Forces and Energy Bands ...

Bonding Forces and Energy Bands in Solids Electrons are controlled to sets of discrete energy levels in atoms, with large gaps among them in which no energy state is obta

Motoring mode of rotating machines, Q. Motoring mode of rotating machines? ...

Q. Motoring mode of rotating machines? The motoring mode has electric power input and mechanical power output. The electromagnetic torque Te drives the machine against the load

Determine the minimum number of poles for the motor, Q. From a three-phase,...

Q. From a three-phase, 60-Hz system, through a motor-generator set consisting of two directly coupled synchronous machines, electric power is supplied to a three-phase, 50-Hz syste

Form factor, Significance of form factor,why we decide the power handing ca...

Significance of form factor,why we decide the power handing capacity in transmission with the help of form factor?

What do you mean by dial pulses, Q. What do you mean by Dial Pulses? D...

Q. What do you mean by Dial Pulses? Dial Pulses: Dial pulsing (many times known as rotary dial pulsing) is the method originally used to transfer digits from a telephone set

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