82.3.1. Overview of Discussion Points

Now, this is this is I should say more practical circuit. Now if I compare the 2 circuits, definitely I am getting higher resistance in this case. But the only drawback here it is the minimum required voltage to get this benefit it is higher namely, for this case we require one V or rather V .

In this chunk, the speaker compares two circuits, noting that the described circuit exhibits higher resistance, which is a beneficial trait in electronic components. However, this advantage comes with a trade-off: the need for a higher minimum voltage to function effectively. The reference voltage, denoted as V_CE(sat), is highlighted as a critical factor in determining the operating efficiency of the circuit.

Consider a situation where you are trying to lift a heavier box with a pulley system. While it’s effective for lifting substantial weights (high resistance), it requires more effort (higher voltage) to get started compared to a simpler system that can lift lighter weights with less effort.

So, minimum required voltage = V here or transistor-3 plus this voltage. And in fact, that voltage if I go through this loop, it can be shown that this voltage and this voltage they are equal. So, that is one V . Whereas for this simple current mirror, the minimum required voltage here it was only V .

This chunk breaks down how to determine the minimum voltage required for the circuit to operate, which is formed by summing the voltage across the transistor and representing it as necessary for circuit functionality. It compares this requirement to a simpler current mirror circuit, which demands a lower voltage to function, emphasizing a key difference in efficiency between the two setups.

Think of a water tank system: if you want to push water to a higher elevation (like needing a higher voltage), you need more energy. Conversely, a simple system where water doesn't need to go as high (less voltage required) can operate more easily, just like the simpler current mirror setup.

So, the other factor, other non-ideality factor, namely, dependency on β you may recall that in the expression of the final current, particularly, for the BJT based circuit there are some loss of the reference current because, it is supplying the I here and I here and the relationship of I with I , it was I = I { }. This is the case for the simple current mirror.

This part delves into another aspect of transistor circuits, particularly addressing the dependency on β (beta), which is the current gain of a transistor. It explains that in certain circuits, particularly in BJT-based designs, there can be a loss of reference current due to the supply : current relationships within the circuit. Understanding this helps in managing how effectively a transistor can amplify signals or currents.

Imagine managing two friends trying to share the same snack. If one friend (the BJT circuit) uses up too much of the wafer, the other might not get enough (current loss). Similar to how we manage resources, current mirrors need to balance these relationships to maintain the overall current supply effectively.

Now, to avoid this loss or to reduce this loss, what we can do? We can place one transistor here, we can place one transistor here, which may work as a current amplifier which is referred as Beta-helper circuit.

This chunk introduces the concept of the Beta-helper circuit, which is aimed at mitigating the losses discussed earlier. By strategically adding another transistor to the circuit, the design can effectively amplify current, thereby reducing the loss experienced by the reference current and improving the circuit's performance. Thus, this method enhances the efficiency of the current mirror.

Think of a relay team in a race where one member can hand off a baton more efficiently. By adding an extra member (transistor) who helps boost the speed of passing the baton (current), the team (current mirror) performs better overall, ensuring that everyone gets their share (current) effectively without loss.

So, the current at the base of this transistor it is ah, I can say this is I . And I = . So, we can say that by adding this extra transistor, the loss of this current loss of this reference current; if I say that is the loss, then that is getting reduced by this factor.

This section discusses how the introduction of an additional transistor modifies the current equations within the circuit. The added transistor helps increase the base current, which ultimately leads to a relationship that decreases overall current loss. The complex equations related to current now include a factor related to the beta of the helper transistor, substantially improving the circuit's efficiency.

Consider a traffic junction where an extra traffic light (the Beta-helper transistor) is added to help regulate flow better. By optimizing how vehicles pass through, it reduces congestion (current loss), allowing for smoother and more efficient movement (current efficiency) throughout the intersection.

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