Confusing yet simple looking problem - DC analysis of diode & xstr

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Discussion Overview

The discussion revolves around a DC analysis problem involving a diode and a transistor, specifically focusing on the bias point and current calculations. Participants are addressing a homework question that requires understanding the behavior of the circuit under DC conditions.

Discussion Character

  • Homework-related, Technical explanation, Debate/contested

Main Points Raised

  • One participant reports an issue with a negative base current, which they describe as impossible, indicating a potential error in their calculations.
  • Another participant emphasizes the importance of showing work to identify errors in the analysis.
  • A different participant advises against using equivalent circuits for DC analysis, suggesting that the focus should be on determining the bias point instead.
  • Hints are provided regarding the emitter voltage if the zener diode is conducting, the implications for emitter current, and the collector voltage.
  • Concerns are raised about the placement of the 0.7V voltage drop in the circuit, questioning whether it is correctly positioned in relation to the resistors.

Areas of Agreement / Disagreement

Participants express differing views on the approach to the problem, with some advocating for specific methods while others challenge those methods. There is no consensus on the correct path forward, and the discussion remains unresolved.

Contextual Notes

Participants have not provided complete calculations or assumptions, which may limit the ability to fully understand the problem. The discussion also reflects uncertainty regarding the validity of certain assumptions about the circuit's behavior.

Cetullah
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Homework Statement


DC analysis is required for the question in attachment.
Vz=6V
B=100
Vbe=0.7V


Homework Equations





The Attempt at a Solution


I tried to find the result using the currents that were defined by the transistor. I found a result that was nonsense, the base current Ib was negative, which is impossible.
Given in the attachment too.

Note: I have an exam tomorrow people. Would be awesome if you have guided me. Thanks :))
 

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It is impossible to tell what you did wrong if you do not show your work...
 
Don't use an equivalent circuit for dc analysis. Equiv. ckts. are for small variations about the bias point. Your job is to find the bias point.

Hints:
what must be the emitter voltage if the zener is on?
so then what must be the emitter current?
so then what is the collector voltage?
was your assumption that the zener is on, valid? why?
 
See where you have placed the 0.7 V voltage drop. Shouldn't it be in 2kilo-ohm resistor branch? Shouldn't there be a short where you have placed the 0.7 volt drop in the above diagram? See this and you can solve.
 
Last edited:

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