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 are the signals used in input control signal, What are the signals use...

What are the signals used in input control signal & output control signal? Input control signal STB (Strobe input) IBF (Input buffer full) INTR(Interrupt request) Ou

Illustrate about full duplex transmission, Q. Illustrate about Full Duplex ...

Q. Illustrate about Full Duplex Transmission? Full Duplex Transmission Data can travel in both directions simultaneously. There is no need to switch from transmit to receive

Discuss crp, Question 1 Explain the construction of telephone network ...

Question 1 Explain the construction of telephone network Question 2 What is out-of-band signaling? Explain Question 3 Describe STP (Signaling Transfer Point) Questio

Thermal considerations, Thermal considerations: At continuous current,...

Thermal considerations: At continuous current, the voltage across the emitter-base junction V BE of a bipolar transistor get decreases 2 mV (silicon) and 1.8mV (germanium) fo

Determine which is the sinusoidal expression for the current, 1. The voltag...

1. The voltage across a 1 - μF capacitor is given. Which is the sinusoidal expression for the current? a) 30 sin200t b) 70cos (800t - 20°) 2. At what frequency will the re

Diode, Hi all i want a conclusion for V-I characteristic curve of Silicon D...

Hi all i want a conclusion for V-I characteristic curve of Silicon Diode (I) using Oscilloscope

Calculate motor efficiency, 1. A self excited shunt generator supplies a lo...

1. A self excited shunt generator supplies a load of 12.5 kw at 125 volts. The field resistance is 25 ohms and the armature resistance is 0.2 ohms. The total voltage drop because o

Tri state devices, Tri State Devices Tri  State  devices have three  st...

Tri State Devices Tri  State  devices have three  states logic 1  logic  0 and high  impedance. A tri state device ( Buffer/ Inverter) has three  lines output  enable as shown

What are tightly coupled systems, What are tightly coupled systems or close...

What are tightly coupled systems or closely coupled systems? In a tightly coupled systems the microprocessor (either coprocessor or independent processors) might be share a com

.branch current method, if a resistor is present between 2 branches in such...

if a resistor is present between 2 branches in such way that its polarities are different to compare with one another so how we choose polarity of that resistor

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