CC amplifier

[maria]

HI,
CAN ANYBODY ANSWER THIS QUESTION? I WILL BE GREATFUL.
THE CONFIGURATION OF COMMON EMITTER AMPLIFIER HAS HIGH INPUT IMPEDANCE AND THAT’S A DISADVANTAGE. I CANT UNDERSTAND THAT WHY IT’S A DISADVANTAGE????

MARIA.

 

[Gene]

All parts and circuits are designed to fulfill a specific purpose. In the case of an amplifier, the design should be selected based on input, output, control function, etc. If, for instance, I wanted to use a 3 volt supply, I would use an amp that was designed to operate at 3 volts - or be easily adaptable. This eliminates the disadvantage of trying to adapt to an inherent problem.

When you say that a part or circuit has disadvantages, that usually means that it it not designed to do your intended job easily. Your statement is pretty broad and seems to assume that just because an amp has a high input Z, it is inherently ALWAYS at a disadvantage. Having no other information, I agree with you - I don't understand.

Now, if the statement was made with the understanding that the high Z amp was being considered for an application for which it is not intended, the statement could well be true.

 

[Roff]

Maria, your question does not match the subject you posted. The common collector (emitter follower) does in general have high input impedance, low output impedance, and near unity voltage gain. In other words, it has current gain. This is not a bad thing.
The common emitter amplifier has generally lower input impedance than the CC, but it has voltage and current gain.
The common base amplifier has low input impedance, high output impedance, and near unity current gain, and voltage gain.
Each configuration has its uses.

Ron