Electronic Devices

Special Purpose p-n Junction Diodes, Junction Transistor

  • A TRANSISTOR transfers current from low resistance circuit to high resistance circuit.
  • EMITTER is heavily doped, moderate in size and supplies majority charge carries to base.
  • BASE is thinnest in size and lightly doped. It allows most of the charge carriers injected in to it to flow into collector without getting neutralized.
  • COLLECTOR is moderately doped, thickest in size and its function is to collect the majority charge carriers from base.
  • p - n - p Transistor:-

  • p-n-p transistor

  • n-p-n transistor

  • n-p-n transistor

  • In a transistor, the direction of arrow on the emitter represents the direction of flow of conventional current.
  • Input resistance in CE configuration of P-N-P transistor is \tt R_{i}=\left(\frac{\Delta\ V_{BE}}{\Delta\ I_{B}}\right)V_{CE}
  • The output resistance in CE configuration of PNP transistor is \tt R_{0}=\left(\frac{\Delta\ V_{CE}}{\Delta\ I_{C}}\right)_{I_{B}}
  •  In CE configuration transistor, the current gain is \tt \beta_{d.c}=\frac{I_{C}}{I_{B}},\beta_{a.c}=\frac{\Delta I_{C}}{\Delta I_{B}}
  • Relation between α, β : \tt \beta = \frac{\alpha}{1-\alpha};\alpha=\frac{\beta}{1+\beta}
  • \tt \frac{1}{\alpha}-\frac{1}{\beta}=1
  • The amplifier which is used to rise the voltage level is called as voltage amplifier. Voltage gain \tt A_{v}=\frac{\Delta\ V_{CE}}{\Delta\ V_{BE}}=\frac{\Delta\ I_{C}}{\Delta\ I_{B}}\times \frac{R_{L}}{R_{i}}=\beta\ \times\frac{R_{L}}{R_{i}}
  • The amplifier which is used to rise the power level is called as power amplifier.
    Power gain (AP) = β AV
    \tt =\beta\times\frac{\Delta\ V_{CE}}{\Delta\ V_{BE}}
  • Power gain (AP) = \tt =\beta^{2}\times\frac{R_{L}}{R_{i}}

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Junction Transistor View the Topic in this video From 00:09 To 13:01

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