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

Find the average power absorbed by each element, Q. Let v(t) = Vmax cos ωt ...

Q. Let v(t) = Vmax cos ωt be applied to (a) a pure resistor, (b) a pure capacitor (with zero initial capacitor voltage, and (c) a pure inductor (with zero initial inductor current)

Basis of the electric solenoid actuator, There is a force on the plunger re...

There is a force on the plunger required to do to move it into or out of the gap and work must be done by or against this force. The conservation of energy dictates that the change

Architecture of 8085 microprocessor, Architecture of 8085 Microprocessor ...

Architecture of 8085 Microprocessor The 8085  microprocessor  is an 8 bit  general purpose microprocessor. 8 bit  processor  means it can  read write  and process 8 bit  data

Explain polymers and their applications, Explain Polymers and their applica...

Explain Polymers and their applications. Polymeric materials or plastics contain a large group of organo or organic metallic high molecules compound. The common properties of s

Explain the working of direct memory access controller, Explain the various...

Explain the various modes in which DMAC works. Working of Direct memory access controller: The modes of operation has demand mode, block mode, single mode and cascade mode.

Di disable interrupts instruction, DI Disable  Interrupts Instruction ...

DI Disable  Interrupts Instruction The interrupt enable  flip flop is reset and all the  interrupts of 8085 microprocessors  except  TRAP  are disabled . the  instruction  form

Determine the duration of the frame, Four voicemessages, each with 3-kHz ba...

Four voicemessages, each with 3-kHz bandwidth, are to be sampled at Nyquist rate, and time- multiplexed with samples taken at twice the Nyquist rate from six analog monitoring sign

Hall effect is associated with which material, Hall Effect is associated wi...

Hall Effect is associated with (A) Conductors. (B) Semiconductors. (C) Thermistors. (D)Solders. Ans: Hall Effect is associated with semiconductors.

Find the antenna temperature, Q. If an antenna has an available noise power...

Q. If an antenna has an available noise power of 1.6 × 10 -15 W in a 1-MHz bandwidth, find the antenna temperature.

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