What is negative logic gate?

What is negative logic gate?

Negative logic: If the signal that activates the logic gate has for its high (1) level a voltage more negative than for its low (0) level then the polarity of the logic is called negative logic, as shown in Fig.

What is the big disadvantage of open collector gates?

One problem with open-collector devices is power consumption, since the pullup resistor dissipates power whenever the output is pulled low, and the higher the desired operating speed, the lower the resistor value (i.e. the stronger the pullup) needs to be, resulting in increased consumption.

What is the disadvantage of pass transistor based logic?

A significant disadvantage of PTL is that the output voltage is lower than the input and it does not allow series connection of a large number of transistors. The addition of a static inverter, Fig. 4, recovers the voltage swing to appropriate values [4].

What is the main disadvantage of TTL devices?

Following points summarize TTL disadvantages over ECL and CMOS: ➨Cosumes more power compares to CMOS family and hence it is not suitable for battery powered devices. ➨It has fan out of 10 which is less compare to CMOS. Logic circuit having N fan out can drive N logic inputs.

What is the meaning of negative logic?

Negative Logic is a logical circuitry in which higher voltage level refers to LOW (‘0’ or FALSE) and Lower voltage level refers to HIGH(‘1’ or TRUE)

What are positive and negative logic gates?

Positive logic is defined as a high voltage level representing a logic 1 and a low voltage level representing a logic 0. Negative logic is the reverse, i.e., a low voltage level represents a logic 1 and a high voltage level represents a logic 0.

What are the disadvantages of basic TTL NAND gate?

1. Noise immunity is not very high; so TTL gates cannot be used in applications where large noise voltages exist. 2. Because of isolation problems, which require more chip space, TTL VLSI circuits are not possible in its conventional form.

What are the advantages and disadvantages of ECL?

➨It has fanout of 25 which is better than TTL and less then CMOS. ➨It has average propagation delay time ( 1 to 4 ns ) better compare to both TTL and CMOS. Hence it is known as fastest logic family.

What are the advantages and disadvantages of using transmission gates over pass transistors?

*The combination of both an PMOS and NMOS in Transmission Gate arrangement avoids the problem of reduced noise margin, increase switching resistance and increased static power dissipation (caused by increased Threshold Voltage), but requires that the control and its complement be available.

What is pass transistor logic list the advantages and disadvantages of it?

This reduces the number of active devices, but has the disadvantage that the difference of the voltage between high and low logic levels decreases at each stage. ADVANTAGES: The advantages of pass-transistor logic are the simple design, the reuse of already available signals, and the low contribution to static power.

What are the advantages and disadvantages of emitter coupled logic?

Following points summarize ECL advantages over TTL and CMOS: ➨It has fanout of 25 which is better than TTL and less then CMOS. ➨It has average propagation delay time ( 1 to 4 ns ) better compare to both TTL and CMOS. Hence it is known as fastest logic family.

What is negative or gate?

An OR gate with inverted inputs is called a negative OR gate, and an AND gate with inverted inputs is called a negative AND gate. In case you’re not persuaded, review for a moment the truth table for a NAND gate: A. B. X.

What are the advantages and disadvantages of logic gates?

The advantages of Logic Gates are: Logical Operations are performed using Boolean Algebra which makes the circuit design more economical and simple. Logic ‘1’ and Logic ‘0’ can be easily distinguished. Disadvantages of Logic Gates

What are the disadvantages of logic circuits?

As logic circuits are the best utilities devices in the modern technology, but there have some disadvantages are as follows; Logic circuits uses more energy than other circuits like analog circuits to accomplish the same tasks resultant circuit produces more heat. This can be limit use of logic circuits.

What are the disadvantages of TTL gates?

TTL gates exhibit low output impedance for high/low states. 1. Noise immunity is not very high; so TTL gates cannot be used in applications where large noise voltages exist. 2. Because of isolation problems, which require more chip space, TTL VLSI circuits are not possible in its conventional form.

What is the function of NOT gate in logic?

NOT Gate NOT gate is the simplest among all the other logic gates. It performs an inversion operation over the single input. Only one terminal is available in NOT, and if the data is 1, the production is 0, and if the input is 0, the output is 1.