The Capacitor and Resistor in parallel have equal impedance at this resonant frequency (1MHz) so when the transistor is operating current is allowed to flow through the RC circuit. At resonant frequency the transistor is said to be switched on i.e 0.7V entering the base and this in turn makes it behave as an amplifier once ac signal ia added to it. R2 and C1 in series act as a high pass filter along with C2 and RL filter out frequencies below our desired range. while Re and Ce act as a low pass filter and cut off high frequencies hence giving us the range of our bandwidth. Capacitors C1 and C2 are also called coupling capacitors as they filter out the DC voltage in our circuit.
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