59.3.4. Bandwidth Extension

The common source amplifier it is primarily it is having a gain of 6 and then upper cut off frequencies 530 kHz, we are not going to calculate the lower cut off frequency primarily because our intention here is to see the enhancement of the bandwidth by the use of common drain stage.

In this segment, we introduce the basics of bandwidth extensions through the use of a common source amplifier. A common source amplifier is given a certain voltage gain and an upper cut-off frequency, which determines how high a frequency signal it can effectively amplify. Here, the gain is 6 and the upper cut-off frequency is 530 kHz. The focus of this discussion shifts towards enhancing this bandwidth by incorporating a common drain stage. This means we intend to find ways to increase the frequency response of the amplifier, allowing it to handle higher frequency signals more effectively.

Imagine you have a water pipe that comfortably carries a certain amount of water (signal) until it reaches a blockage (cut-off frequency). If you add an auxiliary pipe that allows more water to flow around the blockage (common drain stage), you'll increase the total water flow capacity and the system can handle a higher flow rate (bandwidth).

Now, if I call it is f′ it is having 2 candidates to define the upper cut off frequency; one is R . So, this is 2πR and the corresponding load capacitance we do have C . So, if we connect the C here. So, then the upper cut-off frequency it is and yes I do have calculation here, it is 4.24 MHz.

This chunk discusses how cascading the common source (CS) amplifier with the common drain (CD) stage leads to an enhanced upper cut-off frequency. The upper cut-off frequency can be defined in two ways: based on the resistance and the load capacitance connected. The calculations ultimately reveal that this new frequency, f′, is 4.24 MHz, which is significantly higher than the initial cut-off frequency of 530 kHz from just the common source stage. This highlights the effectiveness of combining these stages in amplifier design.

Think of bandwidth like a highway: one lane may be enough to handle regular traffic, but adding an additional lane (common drain stage) allows for much higher speeds and more vehicles (signals) to travel smoothly, thus expanding the capacity or 'bandwidth' of the road.

Now, if I compared these two poles together of course, this is lower. So, the net upper cutoff frequency it is four point, so 4.24 MHz. So, here also the same conclusion it is namely originally the CS common source amplifier it was having a gain of 6 and then it was having a; it was having the upper cutoff frequency it was 580 kHz. Now, we are by the virtue of the common drain stage along with the CS.

In this explanation, we compare the original common source amplifier cut-off frequency (580 kHz) and the newly calculated cut-off frequency after adding the common drain stage (4.24 MHz). The findings assert that while the gain from the common source amplifier remained unchanged at 6, the bandwidth has been significantly enhanced. This comparison solidifies the importance of cascading stages in increasing both gain and bandwidth without compromising performance.

Imagine trying to run a marathon (amplifying a signal). If you train by running short distances, you may only build up to a certain pace (cut-off frequency). But if you start including interval training (adding a common drain stage), you can not only maintain your pace but actually pull ahead, leading to an improved overall performance and finishing time (enhanced bandwidth).

So, this exercise we have done before. So, probably you can calculate what is its voltage gain and the upper cutoff frequency. And then you can compare this with the cell biased CE amplifier sorry cell biased CE amplifier along with say CC stage.

This final topic suggests practical exercises to solidify understanding. Students are encouraged to calculate the voltage gain and upper cut-off frequency of a cell-biased common emitter (CE) amplifier and then compare the results with the combined common collector (CC) stage. This analytical approach fosters hands-on learning, allowing students to see theoretical concepts in action.

Think of this tutorial like a cooking class. Each recipe represents a different amplifier configuration. By trying to make your dish (calculate voltage gain and frequency) and then comparing it to a colleague's dish (comparing amplifier types), you’ll enhance your culinary skills (amplifier design understanding) through practice and analysis.

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