Chapter 4: Difference between revisions

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{| class="wikitable" border="1" style="text-align:center;"
{| class="wikitable" border="1" style="text-align:center;"
|+
|+
! Base-Emitter !! Collector-Base!! Region !! Notes
! Base-Emitter !! Collector-Base!! Region
|-
|-
| FB|| FB || Saturation || <math>I_B>0 </math> and <math> \beta I_B > I_C > 0</math>
| FB|| FB || Saturation
|-
|-
| FB|| RB || Active || <math>I_B>0 </math> and <math> V_{CE}>0.2</math>
| FB|| RB || Active
|-
|-
| RB || FB || Reverse Active
| RB || FB || Reverse Active

Revision as of 12:00, 3 March 2010

Bipolar Junction Transistor

Base, Emitter, Collector
  • NPN: Not Pointing iN
  • PNP: Pointing iN Please
  • The arrow is for the emitter current. For an NPN the current flows into the collector. For a PNP the current flows out of the collector.

How a BJT works

Large-Signal DC models

Base-Emitter Collector-Base Region
FB FB Saturation
FB RB Active
RB FB Reverse Active
RB RB Cutoff
Region NPN PNP
Saturation and and
Active and and
Cutoff and and
  • Active: The normal mode of operation. This mode has the largest common-emitter current gain.
  • Reverse Active: The collector and emitter roles are reversed. Most BJTs are not symmetrical, thus and take on different values.
  • Saturation:
  • Cutoff:
IMG 0288.jpg
IMG 0287.jpg
  • What are the Saturation, Reverse Active and Cutoff regions used for?
  • Why do we always seem to use a common emitter configuration?
  • What does the Reverse Active large-signal model look like? How about graphically?
  • What is the Triode region?
  • For the Saturation region, why is 0.2V the magic number for V_CE?