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

Seal management - meter field testing, Seal Management - Meter Field Testin...

Seal Management - Meter Field Testing For an effective seal management system it is necessary that: i) The  seals  used  are  tamper  proof,  that is they  cannot  be  remo

What do you understand by breakdown diodes, (a) Draw and illustrate the V-I...

(a) Draw and illustrate the V-I characteristics of PN junction diode. How the characteristics reflected with change in temperature? (b) Describe physically why a PN junction dio

Address bus - bus organisation , Address Bus The address  bus is the gr...

Address Bus The address  bus is the group  of 16 lines. It is used  to carry  the address of memory  location and  addresses  of input  and output  ports as shown. It is a unid

Write a report on various types of diodes, a. write a report (at least  2 p...

a. write a report (at least  2 pages ) on various types of diodes( Show and explain  the theory, symbol, circuit, characteristics, data sheets and applications circuits using the d

stack pointer after the pop instruction, What is the position of the Stack...

What is the position of the Stack Pointer after the POP instruction? Ans) The address line is 02 greater than the previous value.

Controls and system, transfer function of Lube Oil Cooler Temperature

transfer function of Lube Oil Cooler Temperature

Hexadecimal to binary conversion , Hexadecimal  to Binary Conversion ...

Hexadecimal  to Binary Conversion Conversion from  hexadecimal  to binary  is the  reverse  of this  process. Express each  hexadecimal  digit  in four bit  binary  equivalent

Explain the working of asynchronous (ripple) counters, Explain the Working ...

Explain the Working of Asynchronous (Ripple) Counters? An external clock is connected to the clock input of the first flip-flop (FF0) only. Thus FF0 changes state at the falli

Show advantages of oscillators, Q. Show Advantages of Oscillators? Alth...

Q. Show Advantages of Oscillators? Although oscillations can be produced by mechanical devices (e.g. alternators), but electronic oscillators have the following advantages:

Data analysis in gis, Data analysis in GIS: Therefore, GIS consists of...

Data analysis in GIS: Therefore, GIS consists of the following: 1.  Database - for storage and retrieval of information. The database forms the foundation of the GIS syst

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