Which statement about TTL and CMOS logic families is true?

The correct statement pertains to the power consumption characteristics of CMOS circuits at higher frequencies. While CMOS logic is known for its low power consumption compared to TTL (Transistor–Transistor Logic) in many applications, as the operating frequency increases, the power consumption of CMOS can approach that of TTL. This is primarily due to the increased switching activity and dynamic power requirements when CMOS gates are toggled at higher speeds. In these scenarios, the leakage currents and capacitive charging/discharging can lead to significant power consumption.

In contrast, TTL circuits tend to have a more constant power consumption regardless of frequency, as they are not as influenced by switching speeds compared to CMOS. Hence, while CMOS circuits typically excel in power efficiency, this advantage diminishes at high frequencies, leading to a scenario where their power use becomes comparable to that of TTL circuits. Recognizing this behavior is essential for designers when selecting logic families for specific applications, especially those that require high-speed operation.