BJT Configurations: CB, CE, and CC

CB, CE, and CC are three common configurations of the Bipolar Junction Transistor (BJT) used in various electronic circuits. Each configuration has its own characteristics and advantages depending on the specific application.

A) CB does not have the Miller effect, hence higher bandwidth:

The Miller effect refers to the capacitance introduced between the input and output terminals of an amplifier due to the voltage gain of the transistor. This capacitance can reduce the bandwidth of the amplifier.

In the CB (Common Base) configuration, the input is applied to the emitter terminal, and the output is taken from the collector terminal. The base terminal is common to both input and output.

The CB configuration does not have voltage gain because the output is taken from the collector, which is a low-impedance terminal. As a result, there is no voltage amplification, and hence, no Miller effect in the CB configuration.

Without the Miller effect, the CB configuration exhibits higher bandwidth compared to the CE (Common Emitter) and CC (Common Collector) configurations. This is because the absence of Miller effect eliminates the capacitance that could limit the bandwidth.

B) CC has the smallest bandwidth:

In the CC (Common Collector) configuration, the input is applied to the base terminal, and the output is taken from the emitter terminal. The collector terminal is common to both input and output.

The CC configuration has a voltage gain less than unity, which means it acts as a voltage buffer. The output voltage follows the input voltage, but with a reduced amplitude. This voltage buffering property of the CC configuration results in a lower bandwidth compared to the other configurations.

C) CB exhibits a reduction in bandwidth due to the Miller effect:

As discussed earlier, the CB configuration does not have the Miller effect. Therefore, it does not exhibit a reduction in bandwidth due to the presence of capacitance between the input and output terminals.

D) CE exhibits an increase in bandwidth due to the Miller effect:

The CE (Common Emitter) configuration has a voltage gain due to the current amplification property of the transistor. This voltage gain results in the Miller effect, where the input and output capacitances cause a reduction in bandwidth.

Unlike the CB configuration, the CE configuration exhibits a reduction in bandwidth due to the Miller effect.

Overall, the CB configuration has the highest bandwidth among the three BJT configurations because it does not have the Miller effect, which can limit the bandwidth of the amplifier.