High side and Low side switching

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Discussion Overview

The discussion revolves around the use of pnp and npn transistors in low side switching applications, particularly in relation to how load characteristics might influence base voltage and current. Participants explore the implications of using different types of transistors for switching in circuits involving components like DC motors.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that pnp transistors are preferred for low side switching because connecting the load to the collector avoids issues with load influence on base voltage, particularly in high voltage drop scenarios.
  • Another participant challenges this view, stating that the explanation sounds backward and expresses confusion about the initial claim.
  • A third participant acknowledges the complexity of the topic and expresses a desire to reinforce their understanding of related concepts like integrated circuits and operational amplifiers.
  • One participant emphasizes the importance of continuously refining and improving one's understanding of new fields, likening the learning process to navigating through fog with solid points of knowledge.

Areas of Agreement / Disagreement

There is disagreement regarding the initial claim about the use of pnp transistors for low side switching, with one participant questioning the reasoning presented. The discussion remains unresolved as participants have not reached a consensus on the topic.

Contextual Notes

The discussion includes varying levels of understanding and assumptions about transistor operation and switching applications, which may affect the clarity and accuracy of the claims made.

Harrison G
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Hello! I just wanted to make sure i get this right. So we prefer to use pnp transistors for low side switch because since then we basicaly connect the load to the collector we don't have to worry that the load(say a dc motor) will influence the base voltage and by influence the base voltage i mean that the load will decrease the current and force us to use higher voltage or lower resistance. Something that is inevitable if you use an npn where a low side switch means to connect the load to the emitter. Is that right? To be clear we are talking about stuff that can cause a large voltage drop on them.
 
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Thank you for the links and excuse me if i made it a bit hard to understand :-D but i got it. I am now learning about Ic's, op amps and such and i felt the need to go back and fortify some old knowledge.
 
Harrison G said:
i felt the need to go back and fortify some old knowledge.

Yes that's the way to do it, constantly refine and improve one's understanding.
I look at any new field as a fog with just a few solid points in it. The focus improves as i learn more vocabulary and understand the ties between those "solid rock anchors".

"The Very Basics rule !"

old jim
 
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