31.1.4. Cascading Amplifiers

So, the next thing is that in case if we are looking for a circuit having this gain, which is higher than the limit of the maximum gain we are achieving from single stage for a given value of V_CC. So, there are two possibilities probably we can replace this resistor by active device, that it will be discussed later. The second possibility or the other possibility is that we can probably cascade to an amplifier to get total gain may be multiplication of the 2 individual stages gain.

Cascading amplifiers is a technique applied when the gain required from a single amplifier stage exceeds its maximum limit. In this context, we can either innovate by replacing passive components, like resistors, with active devices to enhance gain, or we can connect multiple amplifier stages in series, which collectively can provide a higher overall gain. This method hinges on the principle that the total gain of cascaded amplifiers can be obtained by multiplying the gains of the individual stages.

Imagine trying to lift a heavy object. If you can’t lift it by yourself (single amplifier), you can ask a friend for help (cascading amplifiers), where collectively, you can lift the object much more efficiently.

So, say we do have this CE amplifier. So, this is fixed bias, also this is fixed bias and then as I say that individual circuit gained it is upper limit it is only 230 and this is also 230, but if we are looking for higher gain. We simply feed the signal on the output coming from this point and then we feed it to the input here.

In a typical scenario with two cascaded common emitter (CE) amplifiers, each amplifier stage has an upper gain limit (in this case, 230). To achieve a higher overall gain, the output of the first stage is connected to the input of the second stage. The signal amplification process continues as the signal passes through each amplifier, making use of their individual gains to achieve an overall amplification that can be the product of both gains.

Think of a relay race where each runner passes the baton to the next. If each runner (or amplifier stage) can only run a certain limited distance (gain), by linking them together, the total distance covered (overall gain) can far exceed what one runner could achieve alone.

Now, the overall gain, now this V here, V_in1. So, this V_in1 incidentally same as the v. So, we can say that v equals to v × A_1, then A_2 multiplied by this attenuation factor.

The overall gain of the cascaded amplifiers can be calculated by considering the individual gains of each stage and the attenuation introduced by the resistances in the circuit. The formula can be described as: Overall Gain = Gain of Stage 1 × Gain of Stage 2 × Attenuation Factor. This formula helps to realize how the performance of the entire system is defined not only by the individual components but also by how they interact with each other.

Imagine a team of employees working together on a project. If each person (amplifier stage) contributes a certain amount (gain), but they also have to account for communication issues (attenuation), the overall productivity (gain) of the project will depend on both their individual contributions and the effectiveness of their collaboration.

So, while we are cascading we need to be little careful, that the if we are cascading in wrong way, then this attenuation factor it may decrease the overall gain even with respect to individual stage gain.

When designing cascaded amplifiers, it's crucial to maintain an appropriate connection and configuration. If the stages are not designed properly, it can result in negative interaction effects, leading to a reduction in overall gain instead of the expected amplification. Therefore, careful calculations and considerations regarding how each stage interacts with the others are essential to ensure that the intended signal amplification is achieved.

Think of a gourmet kitchen where each chef (amplifier stage) has their specialty. If chefs do not effectively communicate or hand off their tasks properly, the quality or quantity of the meal (overall gain) may suffer. Each chef must work in harmony with the others to create a successful dining experience.

--