Which type of configuration has high output impedance but low input im...
Common Base Configuration
The common base configuration is a type of transistor amplifier configuration where the base terminal is the input, the collector terminal is the output, and the emitter terminal is common to both input and output. In this configuration, the input voltage is applied between the base and emitter terminals, while the output voltage is taken across the collector and emitter terminals.
High Output Impedance
Output impedance refers to the impedance seen by the load connected to the output of the amplifier. In the common base configuration, the output impedance is relatively high. This is because the emitter terminal is common to both input and output, and the emitter current is the sum of the base current and the collector current. As a result, the output impedance is determined by the resistance in the collector circuit, which is typically larger compared to other configurations.
Low Input Impedance
Input impedance refers to the impedance seen by the signal source connected to the input of the amplifier. In the common base configuration, the input impedance is relatively low. This is because the base-emitter junction acts as a forward-biased diode, which has a low dynamic resistance. As a result, the input impedance is determined by the biasing network and is typically smaller compared to other configurations.
Advantages of Common Base Configuration
- High voltage gain: The common base configuration offers a high voltage gain due to the low input impedance and high output impedance.
- Good input-output phase relationship: The input and output signals are in phase in this configuration, which can be advantageous in certain applications.
- High frequency response: The common base configuration exhibits good high-frequency response due to the lower input impedance and the current amplification properties.
Disadvantages of Common Base Configuration
- Low current gain: The common base configuration has a relatively low current gain compared to other configurations.
- Low power gain: The power gain of the common base configuration is lower compared to other configurations.
- Limited voltage swing: The common base configuration has a limited voltage swing due to the forward-biased base-emitter junction.
In conclusion, the common base configuration has a high output impedance but low input impedance. This configuration is commonly used in applications where high voltage gain and good high-frequency response are desired, such as in RF amplifiers and high-frequency oscillators.
To make sure you are not studying endlessly, EduRev has designed Electronics and Communication Engineering (ECE) study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Electronics and Communication Engineering (ECE).