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

Describe common-mode rejection ratio, Q. Describe Common-Mode Rejection Rat...

Q. Describe Common-Mode Rejection Ratio ? When there is a common-mode input voltage, i.e., when the input signals are equal and greater than zero, the output voltage of an idea

Evaluate the efficiency of embedded systems, Questions: a) One common ...

Questions: a) One common characteristic of Embedded Systems is that they need to be dependable. Name and describe any three aspects which encompass dependability. b) Name

Emirrer feedback bias, RE should be made large enough to swamp out rB/ B. h...

RE should be made large enough to swamp out rB/ B. how does making RE large saturate the transistor b

Electrons, Ask question #Minimum 100 words accepted how does the charge pla...

Ask question #Minimum 100 words accepted how does the charge plate relate to the movement of electrons

Application platform requirement - gis technology, Software/Application Pla...

Software/Application Platform Requirement: GIS solutions would primarily consist of Database and Applications software. The application package should work in LAN/WAN/Interne

Calculate the reflection of wedge, The corners of wedge-shaped block are A(...

The corners of wedge-shaped block are A(0,0,2), B(0,0,3), C(0,2,3), D(0,2,2), E(-1,2,2) and F(-1,2,3) and the reflection plane goes the Y-axis at 450 between (-X) & (Z) axis. Calcu

Digital switching switching in telecommunication, Name the switching scheme...

Name the switching schemes used in a digital exchange

Calculate the diameter of an air-filled circular waveguide, Q. Calculate th...

Q. Calculate the diameter of an air-filled circular waveguide? Unlike transmission lines, which operate at any frequency up to a cutoff value, waveguides have both upper and lo

Give the operating modes of 8259a, Give the operating modes of 8259a? (...

Give the operating modes of 8259a? (a) Automatic Rotation (b) End of Interrupt (EOI) (c) Fully Nested Mode  (d) Automatic EOI Mode (e) Specific Rotation (f) Edge

Analog & Digital Filtering, 1) Assume that we are given the continuous-time...

1) Assume that we are given the continuous-time signal xa (t) = xa1 (t) + xa2 (t) + xa3 (t), where, xa1 (t) = 2 + cos3 (2pf1 t + p 3 ) + 2 cos(2pf2 t), xa2 (t) = 2 cos(2pf3 t)

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