Logic Families and Their Characteristics Questions

• Timing definition — output change after input change The time interval between a change at a logic input and the corresponding change observed at the output is called:
• Noise margin calculation — why use worst-case VOH and VOL Why are VOH(min) and VOL(max) (rather than typical values) used when determining logic noise margins?
• Meaning of buffer/driver in logic families Evaluate the statement: “The term buffer/driver signifies the ability to provide low output currents to drive light loads.”
• TTL NAND gate transistor states — all inputs HIGH Using the standard TTL NAND gate schematic (multi-emitter input, phase splitter, totem-pole output), determine the state of each transistor (ON/OFF) when all inputs are HIGH.
• When is a level shifter required in logic interfacing? In mixed-logic designs, under what condition is a level-shifter circuit necessary between two logic families or devices?
• Advantage of Low-Power Schottky (LS) TTL over standard TTL Compared with standard TTL logic, what is a primary advantage of LS (Low-Power Schottky) TTL?
• Emitter-Coupled Logic (ECL) outputs — how can a gate provide both NOR and OR? In ECL logic families, many gates provide a pair of complementary outputs (often labeled Q and Q̄). Explain how the same internal stage can present both a NOR output and an OR output at the pins.
• 4000-series CMOS vs. standard TTL — compare speed and power How does the classic 4000-series CMOS logic (operated at 5 V) compare with the standard TTL logic family in terms of switching speed and power dissipation?
• MOSFET input characteristics — consequence of very high input impedance Which statement best describes the practical effect of the high input impedance of MOSFET-based logic inputs?
• 54XX vs. 74XX TTL logic series — what is the key difference? Compare the 54XX series of TTL logic gates with the 74XX series: which statement best describes the 54XX series?
• ESD-safe handling of MOS devices — identify the statement that is NOT a recommended precaution When working with MOS (especially CMOS) devices, which of the following is NOT a proper electrostatic discharge (ESD) handling precaution?
• Interfacing logic families — can 74HC CMOS directly drive 74ALS TTL? Consider a 74HC-series CMOS gate driving the input of a 74ALS TTL gate at 5 V. Is a direct logic-level interface acceptable without special translation?
• Speed–power product — how do you calculate it for a logic family? Select the correct method for computing the speed–power product (a common figure of merit) of a logic gate or family.
• Interpreting a low speed–power product — what does “lower is better” mean? As a general rule, a logic family with a lower speed–power product is preferable because it offers which combination of characteristics?
• Logic family identifier — which uses a multiemitter transistor at its input? Select the logic family that is historically characterized by a multiemitter NPN transistor on the input stage of its basic gate.
• TTL family naming clarification (74Sxx series) In transistor–transistor logic (TTL), what is unique about the 74Sxx subfamily and why does it enable higher-speed operation compared to standard TTL?
• CMOS handling precautions Why must complementary metal–oxide–semiconductor (CMOS) devices be handled with special care during storage, assembly, and lab work?
• Connecting TTL totem-pole outputs Complete the statement: Totem-pole outputs ________ be connected ________ because ________.
• Totem-pole output behavior in TTL A TTL totem-pole output stage is designed so that the two output transistors:
• TTL logic-level windows Within standard TTL specifications, which range of output voltage is considered invalid (neither guaranteed LOW nor guaranteed HIGH)?