Show which of the following statements about the amplitude limiter is untrue:

Solution(By Examveda Team)

The amplitude limiter is a circuit designed to limit the amplitude of an input signal to a specific threshold. It helps in preventing distortion by restricting the output signal level, even when the input level increases beyond a certain point. Now, let’s analyze each of the options presented:

Option A: The circuit is always biased in class C, by virtue of the leak-type bias.
This statement is untrue. The class of biasing (whether class A, B, or C) depends on the specific circuit design and the way the components are arranged. While a leak-type bias might be used in some circuits, it does not necessarily imply that the circuit is always biased in class C. Class C biasing is typically used for high-frequency operation, and it is not a requirement for all amplitude limiters.

Option B: When the input increases past the threshold of the limiting, the gain decreases to keep the output constant.
This statement is true. The purpose of an amplitude limiter is to keep the output signal at a constant level, regardless of how much the input signal increases. When the input exceeds the threshold, the gain of the circuit is reduced to prevent the output from rising any further, ensuring that it stays within the desired range.
Option C: The output must be tuned.
This statement is not necessarily true. While some amplitude limiters may require tuning, especially in certain radio receiver applications, not all limiters need to be tuned. The function of the amplitude limiter is more about controlling the signal level rather than tuning the output signal. Therefore, the output does not have to be tuned in every case.

Option D: Leak-type bias must be used.
This statement is incorrect. While leak-type bias is used in some circuits for biasing, it is not a mandatory feature for all amplitude limiters. The use of leak-type bias depends on the specific circuit design, but it is not a strict requirement for the function of the amplitude limiter.

In summary, the untrue statement is Option A, as the use of class C biasing is not a universal characteristic of amplitude limiters.