Question

Draw a circuit diagram of a C.E. transistor amplifier. Briefly explain its working and write the expression for (i) current again, (ii) voltage gain of the amplifier

Answer 1

Voltage gain = it is equal the ratio of small change in output voltage at collector to that of change in input voltage

$A_V=\frac{Outputvoltage}{Inputvoltage}$

= $\frac{\Delta V_{CE}}{\Delta V_{EB}}=\frac{\left(\Delta I_C\right)R_{out}}{\Delta I_B{R}_{in}}$

$A_V={\beta }_{AC}\times \frac{R_{out}}{R_{in}}$

Where ${\beta }_{AC}$ is AC current gain

Relation between input and output signals of n-p-n transistor amplifier, when positive half cycle is fed into input circuit, forward bais of emitter base circuit decrease, i.e collector current decrease , output voltage.

$V_o=V_{CE}-I_C{R}_L$

Decrease in collector current cause increase of output voltage.