69.2. CE Amplifier with Active Load

We are talking about CE amplifier with active load and passive load. We discussed and compared their performance. Before we go to CS amplifier, we must make a note of the CE amplifier and the circuit we have discussed particularly its stability issue of its operating point. Next, we will be talking that issue first, then its solution.

This chunk introduces the topic of the CE (Common Emitter) amplifier, particularly focusing on its stability issues. It suggests that both active and passive loads will be discussed in context to the CE amplifier, setting the stage for the upcoming discussion on solutions to the stability problem.

Think of an amplifier like a car's steering system. If the steering is not stable, the car (the signal) may veer off course, causing instability. Similarly, the CE amplifier must maintain a stable operating point to function correctly.

Suppose the early voltage of the two transistors they are not consistent with whatever we have planned and or in case if there is any variation of one of these two bias resistors or maybe β of the 2 transistors if they are changing either with time or whatever it is may be due to temperature or due to aging effect that it will directly affect the operating point here.

This chunk elaborates on how variations in key parameters such as the early voltage, bias resistors, or transistor beta (β) affect the operating point of the CE amplifier. If these parameters change, it can lead to unexpected shifts in the signal amplification process.

Imagine a recipe that requires very precise measurements. If someone uses too much or too little of an ingredient (like the early voltage or bias resistors), the final dish (the output signal) can taste very different than intended.

Let you imagine a case that is suppose all the things are same, but then suppose this early voltage it got changed from say it 100 to maybe 200. Then this voltage if this is getting changed to 200...

In this chunk, we analyze a scenario where the early voltage of a transistor changes from 100 to 200. This change impacts the voltage across the circuit, requiring recalculations to maintain equal current levels in the transistors while ensuring the sum of voltages remains constant.

Consider a team where a player’s performance suddenly changes (like early voltage). The coach (engineer) must adjust the game plan (circuit) to ensure the entire team still works effectively together, even if one member's performance is now different.

The problem it will be even more severe particularly, if β is getting changed and rest of the things are remaining same...

This part discusses how a change in the transistor beta (β) value leads to significant impacts on the operating point. Specifically, if β decreases, the output voltage can drop drastically, highlighting the need for stable operation in the circuit design.

Think of a plant dependent on sunlight for growth. If the sunlight suddenly decreases (like a variation in β), the plant (the output voltage) may suffer, even if everything else (soil, water) remains constant.

To have a stable bias and here we do have the corresponding circuit. If we compare the previous circuit and this circuit, this R instead of connecting to ground, we are connecting to this output node...

In this chunk, we discuss a solution to the stability problem by connecting a bias resistor to the output node instead of ground. This design creates negative feedback, helping to stabilize the output voltage and maintain proper functioning under variable conditions.

This is like adding a counterweight to a teeter-totter; it helps balance the seesaw (circuit), ensuring that small changes in one side do not dramatically affect the overall position of the seesaw.

--