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Kirchoff's Voltage Law

Draw the typi...

Question

Draw the typical input and output characteristic of an $n - p - n$ transistor in $C E$ configuration. Show how these characteristics can be used to determine (a) the input resistance $(r_{i})$ , and (b) current amplification factor $(β)$ .

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Solution

(a) The input resistance of the transistor is defined as the ratio of small change in base - emitter voltage to the corresponding change in base current at a given VCE.

∴ Input impedance, $r_{i} = (\frac{Δ V B E}{Δ I B})_{V C E}$

The input impedance of the transistor in CE mode is very high.

(b) The current amplification factor or current gain is defined as the ratio of a small change in the collector current to the corresponding change in the base current at a constant VCE.

Current gain, $β = (\frac{Δ I C}{Δ I B})_{V C E}$

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Similar questions

(r_{i})

β

(R_{i}

= {[\frac{Change in emitter base voltage (△ V_{B E})}{Change in base current (△ I_{B})}]}_{at constant V_{C E}}

R_{i} = {(\frac{△ V_{B E}}{△ I_{B}})}_{V_{C E}}

(β) = {(\frac{△ I_{C}}{△ I_{B}})}_{V_{C E}}

\frac{△ I_{C}}{△ I_{E} - △ I_{C}}

\frac{\frac{△ I_{C}}{△ I_{E}}}{\frac{△ I_{C}}{△ I_{E}} - \frac{△ I_{C}}{△ I_{E}}}

\frac{α}{1 - α}

\Rightarrow β = \frac{α}{1 - α}

(r_{i})

β

(R_{i}

= {[\frac{Change in emitter base voltage (△ V_{B E})}{Change in base current (△ I_{B})}]}_{at constant V_{C E}}

R_{i} = {(\frac{△ V_{B E}}{△ I_{B}})}_{V_{C E}}

(β) = {(\frac{△ I_{C}}{△ I_{B}})}_{V_{C E}}

\frac{△ I_{C}}{△ I_{E} - △ I_{C}}

\frac{\frac{△ I_{C}}{△ I_{E}}}{\frac{△ I_{C}}{△ I_{E}} - \frac{△ I_{C}}{△ I_{E}}}

\frac{α}{1 - α}

\Rightarrow β = \frac{α}{1 - α}

n - p - n

C E

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