58.1.3. Numerical Examples Discussion

Today, we are going to discuss little more about numerical problems and demonstrating the same conclusion what we have discussed theoretically.

In this chunk, the lecturer introduces the focus of the session: discussing numerical problems related to multi-transistor amplifiers. The aim is to bridge theory with practical numerical examples to solidify understanding. This approach helps students see how theoretical concepts translate into real-world applications, making the learning more tangible.

Consider how learning to ride a bicycle requires theory (understanding how to balance and pedal) and practice (actually riding). Just like in cycling, understanding electronic circuits requires both theoretical knowledge and practical experience through exercises.

We are going to discuss about numerical examples of particularly for CE followed by CC common collector stage to enhance the bandwidth of the amplifier.

Here, the focus is on two configurations: Common Emitter (CE) and Common Collector (CC). These configurations are critical in enhancing the bandwidth of amplifiers. The lecturer emphasizes that by alternating between these configurations, students will better understand how each component contributes to overall performance, particularly in changing the frequency response of the amplifier.

Think of a sports team that changes strategies based on the opponent's strengths. Just as a team needs different plays to address various situations, engineers manipulate amplifier configurations to achieve optimum bandwidth to handle different signals.

This slide is a recapitulation of one of our previous numerical examples where we have discussed about CE amplifier having fixed bias arrangement and different parameters are given here including the supply voltage of 12 V, then device parameters including β of the transistor, early voltage, ...

In this chunk, the lecturer recaps previous discussions on a CE amplifier with a fixed bias arrangement and lists the parameters such as supply voltage and transistor properties. Understanding these parameters is essential as they directly impact the performance of the amplifier. For students, recognizing how these values interplay will help in solving numerical problems effectively.

Imagine constructing a building; you need to know the dimensions of each room (parameters) and the overall structure (fixed bias) to ensure it stands strong. Similarly, in circuit design, knowing the parameters helps in creating a robust amplifier.

Let us try to see the operating point of the transistor. ... So, we can say that V – V = I × R. ... So, it is value it is now 20 µA.

This section details the calculation of the transistor's operating point using KCL (Kirchhoff's Current Law). It walks the students through deducing the values needed to find the bias current which is essential for amplifying signals in the transistor. By understanding how to calculate these values, students can predict the behavior of the amplifier in practical scenarios.

Consider a water tank system; understanding how much water flows in and out (currents) allows you to predict whether the tank will overflow or run dry. In circuits, calculating currents accurately ensures the amplifier functions as intended.

Now, we obtained the small signal parameters value namely g ... and from that we can get the voltage gain. ... So, that is the gain we are getting.

After calculating the operating point, the next step involves finding small signal parameters which are crucial for determining the voltage gain of the amplifier. The relationship between these parameters defines the efficiency and response of the amplifier to varying input signals. An understanding of these parameters provides students with the tools to gauge amplifier performance under different conditions.

Think of tuning a radio; adjusting the frequency helps get a clearer signal (gain). In amplifiers, tweaking small signal parameters fine-tunes how well the amplifier reproduces the input signal.

Now, for our main focus to demonstrate how the bandwidth it will be extended we can probably calculate only the upper cutoff frequency ... this gives us I have done the calculation for you. So, this is coming 513 kHz.

The upper cutoff frequency is a key aspect of amplifier design that describes the highest frequency the amplifier can effectively handle. Here, the lecturer demonstrates how to calculate it using resistance and capacitance values. This calculation is vital for understanding the limitations of an amplifier in processing signals of different frequencies.

Just as a pair of headphones has a limit on how high or low the sounds they can reproduce (cutoff frequencies), amplifiers also have frequency limits that determine their usability for different audio signals.

So in summary what we have circuit performance ... So, the exercise we are going to do it is that we are going to put in this case instead of putting the capacitor ...

In this segment, the focus shifts to assessing the impact of introducing a common collector stage on the bandwidth of the amplifier. By comparing configurations with and without this stage, students can visualize the enhancements in bandwidth. This exercise reinforces the principles discussed earlier about amplifier configurations.

It's similar to adding lanes to a highway; more lanes allow more cars to travel simultaneously, increasing traffic flow (bandwidth) without sacrificing speed (gain). Adding a CC stage improves the amplifier's capability to handle more frequencies simultaneously.

--