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Thermal considerations:
At continuous current, the voltage across the emitter-base junction VBE of a bipolar transistor get decreases 2 mV (silicon) and 1.8mV (germanium) for every 1°C rise in temperature (reference being 25°C). Through the Ebers-Moll model, if the base-emitter voltage VBE that is held constant and the temperature increases, the current by the base-emitter diode IB will raise, and so the collector current IC will as well increase. Depending upon the bias point, power dissipated in the transistor might as well increase that will further increase its temperature and exacerbate the problem. This deleterious positive (+ive) feedback results in thermal runaway. There are various approaches to mitigate bipolar transistor thermal runaway. For instance,
1. Negative feedback can be made into the biasing circuit so that increased collector current directs to decrease base current. Therefore, the increasing collector current throttles its source.
2. Heat sinks can be employed which carry away extra heat and prevent the base-emitter temperature from rising.
3. The transistor can be biased that is why its collector is usually less than half of the power supply voltage that implies that collector-emitter power dissipation is at the maximum value of it. After that runaway is impossible because increasing collector current directs to a decrease in dissipated power; this notion is termed as the half-voltage principle.
The circuits below primarily illustrate the use of negative feedback to avoid thermal runaway.
Consider the circuit of Figure and obtain the complete solution for the voltage v C (t) across the 5-F capacitor and the voltage vx(t) across the 5- resistor.
Q. If a single phase motor fails to run or start slow what action to be taken. Ans: If it is not starting check the supply and test the winding if it found normal check
Jump Instruction There are two types of jump instruction unconditional jump conditional jumps
are you able to help with power system
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Q. A current of 65 A is measured with an analog ammeter having a probable error of ± 0.5% of full scale of 100 A. Find the maximum probable percentage error in the measurement.
having looked at the circuit, i first wanted to start my frequency from 0 and plot for 10000 to 20000. so in matlab i used f = 0:10000:20000; but the equation for frequency is f= 1
why Vout begins to decrease ...
Output Characteristics The output or drain characteristic of N - Channel power MOSFET. When gate is made positive with respect to the source an N type channel is formed
Explain Stator of a Synchronous Machine? The stator of a synchronous machine is made of thin laminations of highly permeable (silicon) steel in order to reduce the core losses.
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