In a common emitter amplifier circuit using an

In common emitter amplifier circuit input and out put voltage are out of phase. When input voltage is increased then $\mathrm{i}_{\mathrm{b}}$ is increased, $\mathrm{i}_{\mathrm{c}}$ also increases so voltage drop across $\mathrm{R}_{\mathrm{c}}$ is increased. However increase in voltage across $R_{C}$ is in opposite sense.