a) The CE amplifiers are used in applications where high gain is required. It can be used as single stage or in cascade.
a) CB amplifiers have better frequency response than CE amplifier. It is used as high frequency amplifier combined with common emitter amplifier. Its low input resistance finds application in specific areas where the signal strengths are very low (or) when load on source should be very low.
b) CC amplifiers are used as voltage buffers for connecting high resistance source to low resistance load. It is used as output stage in multistage amplifier because of its low output resistance.