Which of the following logic gates can be used to implement the functionality of any logic gate? A universal gate is the one with which any other Boolean function can be implemented without the need of other gates.
In this gate, output of logic gate is false only when both the inputs are true. It is the complement of AND gate. NOR gate: Output of this logic gate is true when both inputs are false. If A and B are logical inputs to the following circuit, determine the logical relation between the inputs and the output C.
C output. Propagation delay :. It is the time required for a digital signal to travel from the input s of a logic gate to the output ad is denoted by t pd. In the case of a digital IC, the propagation delay of a gate is the average transition time that a signal takes from input to output, i.
Units — ns nanoseconds i. Start Learning. Get proficient with the Digital Electronics concepts with detailed lessons on the topic Logic Families among many others.
CMOS has the highest fan-out among the given logic families. Concept: In a Common Emitter transistor, if input A is at low potential Logic0 than, there is no voltage drop across Base Emitter junction and hence no current will flow through the Transistor Cut Off state.
In a Common Emitter transistor, if input A is at high potential Logic1 than, there will be a voltage drop across Base Emitter junction and hence current will flow through the Transistor Saturation state.
Get Started for Free Download App. Answer Detailed Solution Below Option 1 : 1. Concept: Noise Margin It is the amount of noise that can be allowed without disturbing the normal operation of the logic gates. TTL logic has very low power consumption and is therefore widely used in highly integrated components TTL devices have logic levels of about 3.
Answer Detailed Solution Below Option 1 : TTL logic has very low power consumption and is therefore widely used in highly integrated components. The most important parameters for evaluating and comparing logic families are: Power dissipation Propagation delay Noise margin Fan-out loading General comparison of three commonly available logic families is explained in the following table: Logic Family Advantages Disadvantages CMOS Lowest power consumption Used in all microcomputer chips today.
Most common logic family. Easily damaged by static discharge and voltage spikes. TTL Earliest developed. Most rugged. Least susceptible to electrical damage. Concept : The terms positive logic and negative logic refer to two conventions that tell the relationship between logical values and the voltages used to represent them. Positive Logic Convention: In this, the more positive potential is considered to represent true or logic 1, and the more negative potential is considered to represent false or logic 0.
Negative Logic Convention: In this, the more negative potential is considered to represent true or logic 1, and the more positive potential is considered to represent false or logic 0. Calculation: Two voltages are given -2 V and -1 V As we have to represent them in the positive logic convention: -2 V will represent logic 0 as it is more negative and -1 V will represent logic 1. Hence option 3 is the correct answer. Gain and bandwidth Propagation delay time and power dissipation Fan-out and propagation delay time Noise margin and power dissipation.
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This means that the current draw of CMOS devices increases with switching rate controlled by clock speed, typically. However, because the logic thresholds of CMOS were proportional to the power supply voltage, CMOS devices were well-adapted to battery-operated systems with simple power supplies. CMOS gates can also tolerate much wider voltage ranges than TTL gates because the logic thresholds are approximately proportional to power supply voltage, and not the fixed levels required by bipolar circuits.
The required silicon area for implementing such digital CMOS functions has rapidly shrunk. The extremely small capacitance of the on-chip wiring caused an increase in performance by several orders of magnitude. On-chip clock rates as high as 4 GHz have become common, approximately times faster than the technology by CMOS chips often work with a broader range of power supply voltages than other logic families.
Lowering the supply voltage reduces the charge stored on any capacitances and consequently reduces the energy required for a logic transition. Reduced energy implies less heat dissipation. By lowering the power supply from 5V to 3. Many motherboards have a voltage regulator module to provide the even lower power supply voltages required by many CPUs.
Because of the incompatibility of the CD series of chips with the previous TTL family, a new standard emerged which combined the best of the TTL family with the advantages of the CD family. It could be used both with logic devices which used 3. Interconnecting any two logic families often required special techniques such as additional pull-up resistors, or purpose-built interface circuits, since the logic families may use different voltage levels to represent 1 and 0 states, and may have other interface requirements only met within the logic family.
These devices only work with a 5V power supply. With HC and HCT logic and LS-TTL logic competing in the market it became clear that further improvements were needed to create the ideal logic device that combined high speed, with low power dissipation and compatibility with older logic families.
A whole range of newer families has emerged that use CMOS technology. A short list of the most important family designators of these newer devices includes:. Not shown are some early obscure logic families from the early s such as DCTL direct-coupled transistor logic , which did not become widely available. Propagation delay is the time taken for a two-input NAND gate to produce a result after a change of state at its inputs.
Toggle speed represents the fastest speed at which a J-K flip flop could operate.
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