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General Knowledge
Verbal Reasoning
Computer Science
Interview
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Logic Families and Their Characteristics Questions
Interfacing logic families with different VCC — appropriate solution When two IC logic families operate at different supply voltages (VCC), which interface component is typically used to ensure correct logic-level translation?
CMOS dynamic power — why frequency matters for dissipation Why is the operating frequency a critical factor in determining power dissipation for CMOS logic?
Lowest propagation delay among logic families Which logic family is known for the shortest propagation delay (i.e., the fastest switching) among the options below?
Understanding PMOS and NMOS logic families PMOS and NMOS logic families primarily:
Interfacing TTL outputs to CMOS inputs — solving VOH(min) mismatch If the VOH(min) of a TTL IC is too low to meet the VIH(min) requirement of a CMOS input, what is the usual simple fix?
Non-saturating logic family — avoiding transistor saturation Which logic family is characterized by operation that prevents transistor saturation during switching?
Emitter-Coupled Logic (ECL) — Identify the key characteristics Which of the following choices best summarizes the important features of emitter-coupled logic (ECL) families, considering typical operating practice (negative supply rails), voltage swing, speed, noise margins, and power?
TTL Best Practice — Why a decoupling capacitor is needed and where to connect it In transistor–transistor logic (TTL) circuits, what is the purpose of a local decoupling (bypass) capacitor and where should it be connected for best results?
Open-Collector Outputs — Source vs. sink capability Complete the statement correctly: An open-collector output can ________ current, but it cannot ________.
TTL Output Drive — Compare sourcing at HIGH vs. sinking at LOW Evaluate the statement: “The TTL HIGH-level source current is higher than the LOW-level sinking current.” Is it true or false in standard TTL practice?
Common TTL Series Identification — Which family code is most prevalent? Among the listed options, select the designation that refers to the classic, widely used TTL logic IC series.
Pulse Edges — Standard definitions of rise time (tr) and fall time (tf) Fill in the standard reference levels used to define a pulse’s rise and fall times: tr is measured from ________ to ________; tf is measured from ________ to ________.
Fan-Out in TTL — Define “ten TTL loads per TTL driver” In standard TTL terminology, the phrase “ten TTL loads per TTL driver” refers to which specification?
Open-Collector Gates — Purpose of the pull-up resistor Why is an external pull-up resistor required when using an open-collector logic gate output, and what does it provide to the node?
TTL NAND Gate (All Inputs LOW) — Transistor conduction states In a standard TTL NAND gate with a totem-pole output, if all inputs are at LOW level, which ON/OFF combination for the internal transistors (Q1 through Q4) is correct?
IC Power Dissipation from Supply Current — Average ICC method An IC operates from VCC = +5 V with ICC in HIGH state (ICCH) = 10 mA and ICC in LOW state (ICCL) = 23 mA. Assuming a 50% duty cycle, what is the chip’s average power dissipation?
Fan-out calculation for logic families In digital design, fan-out is determined by calculating how many standard inputs an output can drive in both the HIGH and LOW states, and then taking which result and from which ratios?
TTL-to-CMOS interfacing — reason for a pull-up resistor When connecting a TTL output to a CMOS input (same nominal VCC), why is a pull-up resistor commonly added on the TTL output line?
Naming the HIGH-state output current for a 7400 NAND gate The output current capability of a single 7400 NAND gate in the HIGH state is referred to as:
Best practice for unused TTL gate inputs What should be done with unused inputs on TTL logic gates to ensure reliable operation and prevent noise or extra power draw?
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