PNP Transistor voltage calculation

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SUMMARY

The discussion centers on the voltage calculations for PNP transistors, specifically the differences in calculating the collector-emitter voltage (Vce) in two scenarios. In part A, the base-emitter voltage drop (0.7V) is ignored due to the assumption of infinite current gain (βf), while in part B, it is considered because the transistor operates near saturation. The confusion arises from the diagram depicting an NPN transistor instead of a PNP, highlighting the importance of accurate component representation in circuit analysis.

PREREQUISITES
  • Understanding of transistor operation, specifically PNP and NPN types.
  • Familiarity with voltage drop across diodes, particularly the base-emitter junction (0.7V).
  • Knowledge of current gain (βf) in bipolar junction transistors.
  • Basic principles of circuit analysis, including saturation conditions.
NEXT STEPS
  • Study the differences between PNP and NPN transistor configurations.
  • Learn about the impact of current gain (βf) on transistor operation.
  • Research the conditions for transistor saturation and cutoff.
  • Examine practical examples of voltage calculations in transistor circuits.
USEFUL FOR

Electronics students, circuit designers, and engineers working with bipolar junction transistors who need clarity on voltage calculations and transistor behavior in different configurations.

vizakenjack
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For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored?

Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken into account? I get that if βf = infinite, and βf = ic/ib ib -> 0
 
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The thread title refers to PNP but the diagram shows NPN. What gives?

What is the origin of the image you inserted? How reliable is it?

In the first circuit base bias comes from the collector voltage so it limits the lowest voltage on the collector with Vc > Vb.
In the second case the transistor is being modeled on the edge of saturation with Vc = Vb.
 

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