 # 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}}

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

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