Common emitter vs. common collector power amplification

In summary, the conversation discussed the differences between common emitter and common collector configurations in transistor amplifiers. It was mentioned that the common emitter is often preferred as it produces more power due to its higher current gain. However, the common collector also has its advantages, such as a higher voltage gain. Ultimately, both current gain and voltage gain are important in determining power gain.
  • #1
kthouz
193
0
Hello everybody!
I was studying stuff about transistor and i got stuck somewhere. In lecture they said that The common emitter is the more likely configuration used to amplify signals because it produces more power than other configurations. But when i tried to understand it clearly if found that in a common emitter configuration the input base current Ib is multiplied by [tex]\beta[/tex] (the current gain factor) to give an output collector current Ic=[tex]\beta[/tex]Ib while as far as common collector configuration concerned, the input base current is multiplied by (1+[tex]\beta[/tex]) giving an output emitter current Ie=(1+[tex]\beta[/tex])Ib. As we know the power is directly dependent on the current (P=UI), so i can conclude saying that the power due to a common collector configuration is higher than the one due to a common emitter configuration since the Ie=(1+[tex]\beta[/tex])Ib[tex]\geq[/tex]c=[tex]\beta[/tex]Ib . Am I right?
 
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  • #2
The *current* gain is nearly equal for CC & CE. But the *voltage* gain is >> 1 for CE, but just under 1 for CC. The *power* gain is the product of current gain & voltage gain. The CE has greater *power* gain than the CC.

Claude
 
  • #3
Then the great part of power is from the voltage. Now i understand.Thank you!
 
  • #4
Well, as far as power goes, it's the product of both current & voltage. One is not "greater". For a CB stage, the current gain is just under 1, while the voltage gain >> 1. So with the CB & CC stages, power gain is less than that of the CE stage. The CE has a current gain >> 1, as well as a voltage gain >> 1. This is why the CE has such great power gain.

The current gain & voltage gain are equally important as far as power gain is concerned.

Claude
 

FAQ: Common emitter vs. common collector power amplification

What is the difference between common emitter and common collector power amplification?

Common emitter and common collector are two different configurations of transistor-based power amplifiers. In common emitter, the input signal is connected to the base of the transistor, while in common collector, it is connected to the emitter. This results in different voltage and current gains for the two configurations.

Which configuration is more commonly used for power amplification?

The common emitter configuration is more commonly used for power amplification. This is because it has a higher voltage gain and a higher input impedance, making it more suitable for amplifying weak signals.

What are the advantages of using a common collector configuration?

The common collector configuration has a very high current gain, making it ideal for driving low impedance loads. It also has a very low output impedance, allowing it to provide a nearly constant output voltage even when the load changes.

Can the common emitter and common collector configurations be combined?

Yes, the common emitter and common collector configurations can be combined to create a common emitter follower circuit. This circuit has the advantages of both configurations - high voltage gain from the common emitter and high current gain from the common collector. It is often used for impedance matching between stages in a multi-stage amplifier.

Which configuration is more suitable for audio amplification?

The common emitter configuration is more suitable for audio amplification because it has a wider frequency response and can handle larger input signals without distortion. The common collector configuration is better for low frequency amplification, such as in radio frequency circuits.

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