RAJASTHAN PMT Rajasthan - PMT Solved Paper-2007

  • question_answer
    The relation between amplification factor \[(\mu ),\] plate resistance \[({{r}_{p}})\]and mutual conductance \[({{g}_{m}})\]of a triode valve is given by

    A)  \[\mu ={{r}_{p}}\times {{g}_{m}}\]                        

    B)  \[{{r}_{p}}=\mu \times {{g}_{m}}\]

    C)  \[{{g}_{m}}=\mu \times {{r}_{p}}\]        

    D)         none of these

    Correct Answer: A

    Solution :

    The amplification factor \[\left( \mu  \right)\] is given by                 \[\mu ={{\left( \frac{\Delta {{V}_{P}}}{\Delta {{V}_{g}}} \right)}_{{{I}_{P}}=\operatorname{constant}}}\]                                ? (i) Plate resistance                 \[{{r}_{P}}={{\left( \frac{\Delta {{V}_{P}}}{\Delta {{I}_{g}}} \right)}_{{{V}_{g}}=\text{constant}}}\]                            ? (ii) Transconductance                 \[{{g}_{m}}={{\left( \frac{\Delta {{I}_{P}}}{\Delta {{V}_{g}}} \right)}_{{{V}_{P}}=\text{constant}}}\]                          ? (iii) \[\therefore \]  \[\mu =\frac{\Delta {{V}_{p}}}{\Delta {{V}_{g}}}=\frac{\Delta {{V}_{P}}}{\Delta {{I}_{P}}}\times \frac{\Delta {{I}_{p}}}{\Delta {{V}_{g}}}\] From Eqs. (ii) and (iii), we get                 \[\mu ={{r}_{p}}\times {{g}_{m}}\]


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