Understanding KVL Loop in BJT Biasing and Calculating Ve: A Guide

In summary, the conversation discusses the calculation of Ve and the confusion about its positive value. It is clarified that Ve is the emitter voltage relative to ground and does not necessarily have to be positive. The concept is further explained using an NPN transistor and Kirchoff's Voltage Law. Additionally, the conversation mentions the application of KVL in an open loop and the use of an AC input for an audio amplifier.
  • #1
karandeepdps
3
0
thread moved into homework forum, so comes without template
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Screen Shot 2015-10-02 at 2.48.17 pm.png
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Please help how Ve is calculated what i think is that it should be:
-Ve=-Vee+IeRe;
How Ve is taken positive please someone draw equivalent circuit for same
 
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  • #2
VE is defined as the emitter voltage wrt ground. Nothing about this says that VE must turn out to be a positive voltage, though. You can see that VE will be somewhere between -VEE and +VCC.

If NPN emitter current is the current out of the transistor emitter, then the upper end of RE is the more positive. Draw arrows to show current direction, and voltage drop across resistances, and apply Kirchoff's Voltage Law.
 
  • #3
Thanks will you please help me in this question also i am confused in Vcc equations
Screen Shot 2015-10-02 at 6.47.15 pm.png
 
  • #4
Explain which line in the solution you are having trouble with.
 
  • #5
Last line,how they have applied kvl to an open loop.
 
  • #6
karandeepdps said:
Last line,how they have applied kvl to an open loop.
There is no open loop.

RB is supplying base current from the positive rail, VCC. Because the transistor is operating in the active region, its base is forward biased and its B-E potential is labelled VBE.

The wire from the base ending in mid-air simply indicates where the amplifier's AC input will be impressed when the circuit is later completed to function as an audio amplifier, for example.
 

1. What is KVL loop in BJT biasing?

KVL loop in BJT biasing refers to the application of Kirchhoff's Voltage Law in the analysis of a bipolar junction transistor (BJT) circuit. It involves tracing the path of voltage drops in a closed loop within the circuit to determine the voltage across each component.

2. Why is KVL loop important in BJT biasing?

KVL loop is important in BJT biasing because it allows us to accurately calculate the voltages at various points in the circuit. By following the voltage drops in a closed loop, we can determine the proper biasing conditions for the transistor and ensure it operates within its desired range.

3. How do you apply KVL loop in BJT biasing?

To apply KVL loop in BJT biasing, you first need to identify the closed loop in the circuit. Then, starting from any point in the loop, assign a direction of current flow and label the voltage drops across each component according to this direction. Finally, use Kirchhoff's Voltage Law to set up and solve the equations for the loop.

4. Can KVL loop be used for both NPN and PNP transistors?

Yes, KVL loop can be used for both NPN and PNP transistors. However, the direction of current flow and the polarity of the voltage drops will be opposite for these two types of transistors. It is important to keep this in mind when applying KVL loop in BJT biasing for different transistors.

5. What are the limitations of KVL loop in BJT biasing?

KVL loop is based on the assumption that the voltage drops across each component in the loop are known. However, in real-world circuits, these voltage drops may vary due to factors such as temperature and manufacturing tolerances. Therefore, KVL loop may not always provide completely accurate results and should be used in conjunction with other analysis methods to ensure accurate biasing of the BJT.

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