The true meaning of voltage drop

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SUMMARY

The discussion focuses on the concept of voltage drop in CE amplifiers with negative feedback, specifically how an increase in emitter current (IE) through the emitter resistor (RE) affects the emitter voltage (VE). As the current increases, the voltage drop across RE also increases, making the emitter more positive. This phenomenon is explained through the relationship defined by Ohm's Law (V=IR), emphasizing that voltage is a potential difference that drives current, rather than being caused by it. The participants clarify that voltage drop is a physical quantity representing the potential difference across a resistor, and it is crucial to understand the underlying principles of electrical fields and current flow.

PREREQUISITES
  • Understanding of CE amplifier configurations and negative feedback mechanisms.
  • Familiarity with Ohm's Law (V=IR) and its application in circuit analysis.
  • Basic knowledge of electrical concepts such as voltage, current, and resistance.
  • Awareness of the role of resistors in circuits and their impact on current flow.
NEXT STEPS
  • Study the effects of negative feedback in transistor amplifiers to enhance circuit stability.
  • Learn about the physical principles of electric fields and their role in current flow through resistors.
  • Explore advanced topics in circuit theory, such as Kirchhoff's laws and their applications.
  • Investigate the relationship between power, voltage, and current in resistive circuits.
USEFUL FOR

Electronics students, circuit designers, and engineers looking to deepen their understanding of voltage behavior in transistor amplifiers and improve their circuit analysis skills.

  • #31
jim hardy said:
So hydraulic analogy is useful to get your brain accustomed to working circuits "in your head" .
old jim

Yes - I fully agree.
As an interesting exercise, one could try to explain the amplifying properties of a transistor using the hydraulic analogy - in particular, if it seems to be possible that a tiny flow of water is able to control (with gain !) the water flow of a much larger river.
 
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  • #32
LvW said:
if it seems to be possible that a tiny flow of water is able to control (with gain !) the water flow of a much larger river.
Pressure actuated valve on a much larger flow pipe? (Ah, this would be a FET)
 
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  • #33
Voltage is work done per unit charge , therefore when we say voltage drop work is done between the resistor ie really a energy loss ,and it is physical quantity
 
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  • #34
You have to be careful using purely conceptual thinking with physics. Sometimes things behave in a way that's not intuitive. On the the other hand, the math does not always clarify dependencies such as the fact voltage has to be present before current will flow. Usually you need to understand the math first to understand the behavior conceptually. We use the term Voltage drop in a practical catch all manner, but the term fails to provide a sense of what's really going on there. The outward appearance is a voltage differential between one node and another, but there's physical behaviors taken for granted that result in those observable measurements.
 
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  • #35
CraigHB said:
We use the term Voltage drop in a practical catch all manner, but the term fails to provide a sense of what's really going on there.

"Voltage drop" is almost slang for voltage across something that is removing energy from a circuit, ie a load such as a motor or lamp
curiously
it's rare to hear the converse term "Voltage rise" describing voltage across something that deposits energy ie a source such as a battery or power supply.
 
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  • #36
Thanks everyone, your help is very helpful!
 

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