For CE transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 4V. If the current amplification factor of the transistor is 100 and the base resistance is 1 kΩ, then the input signal voltage is
20 mV
Output current, IC=VCRC=42000=2 mA
Now, base current, IB=ICβ=2 mA100=20 μA
So, input voltage, VB=IBRB=20 μA×1 kΩ=20mV