Electronics Engineering (ELEX) Board Practice Exam

Which low-frequency cutoff does not primarily determine the low-frequency response for a complete system?

1. C_E

2. C_S

3. C_C

4. Highest cutoff

The correct answer is: Highest cutoff

The correct choice indicates that the "highest cutoff" does not primarily determine the low-frequency response for a complete system. In many electronic circuits, particularly those involving amplifiers or filters, the low-frequency response is primarily influenced by components like coupling capacitors and bypass capacitors. The term "highest cutoff" typically refers to the highest frequency point where the system is still able to effectively pass signals. This is relevant for high-frequency responses rather than low-frequency performance. In contrast, low-frequency response is shaped by the interaction of capacitors and resistors that create a first order filter effect, where each component's capacitance can introduce a low-frequency cutoff point. When analyzing low-frequency behavior, capacitors such as coupling capacitors (C_C) and emitter or source capacitors (C_E and C_S, respectively) play crucial roles in defining the overall low-frequency cutoff by determining how low of a frequency can successfully pass through the system without significant attenuation. Therefore, it is the specific values of the capacitors in the circuit that influence the low-frequency characteristics, while the highest cutoff pertains to the overall system bandwidth, which is not directly tied to the low-frequency response specifically. This understanding clarifies why the highest cutoff does not primarily dictate low-frequency behavior.