What should be done to unused inputs on TTL gates? They should be left disconnected so as not to produce a load on any of the other circuits and to minimize power loading on the voltage source. All unused gates should be connected together and tied to V through a 1 k resistor.
What must you do to unused inputs on a logic gate chip?
74HC/HCT: What to do with unused inputs and why?
- connect them directly to Vcc.
- connect them directly to GND.
- connect them to Vcc through a pull-up resistor.
- connect them to GND through a pull-down resistor.
Do we need to ground the unused input for AND gate?
To ensure that the gates are not left floating they should be connected either to ground or to the supply rail. Often it will not matter which is used, unless it is an input on a used function when the required input, either high or low would mean connecting it to the supply rail or ground respectively.
What is the range of invalid TTL output voltage?
10. What is the range of invalid TTL output voltage?
Exercise :: Logic Families and Their Characteristics – General Questions.
| A. | 0.0–0.4 V |
|---|---|
| B. | 0.4–2.4 V |
| C. | 2.4–5.0 V |
| D. | 0.0–5.0 V |
What is unique about TTL devices such as the 74SXX?
What is unique about TTL devices such as the 74SXX? These devices use Schottky transistors and diodes to prevent them from going into saturation; this results in faster turn-on and turn-off times, which translates into higher frequency operation.
Why should unused inputs be handled properly?
Because CMOS logic has a very high input impedance, any open input might result in a false output value due to the influence of a surrounding electric field.
What is unused input?
Real unused logic inputs are ones whose logic state does not affect the particular application required—these should be connected to fixed Logic 0 or Logic 1 potentials and not left floating6.
Can AND gate have 3 inputs?
Like the AND gate, the OR function can have any number of individual inputs. However, commercial available OR gates are available in 2, 3, or 4 inputs types. Additional inputs will require gates to be cascaded together for example.
When A AND B are inputs output of OR gate is?
Detailed Solution. The output of AND gate is given as AB hence its value is logic 1 when both inputs A and B are logic 1’s.
What conditions are required for a three input AND gate to have its output on?
Rule for an AND gate: output is “high” only if first input and second input are both “high.” Rule for an OR gate: output is “high” if input A or input B are “high.” Rule for a NAND gate: output is not “high” if both the first input and the second input are “high.”
What is fan in logic gate?
Fan-in is a term that defines the maximum number of digital inputs that a single logic gate can accept. Most transistor-transistor logic ( TTL ) gates have one or two inputs, although some have more than two. A typical logic gate has a fan-in of 1 or 2.
Why is a pull up resistor needed for an open collector gate?
A pull-up resistor is a resistor used to keep a given point in a circuit HIGH when in the active state. Why is a pull-up resistor needed when connecting TTL logic to CMOS logic? An open collector output can current, but it cannot . A universal logic gate is one, which can be used to generate any logic function.
Can a 74hcmos logic gate directly connect to a 74alsttl gate?
Correct Answer: They are simply the inverse of each other.
What must be done to interface TTL to CM?
7. What must be done to interface TTL to CMOS? Explanation: To interface TTL to CMOS a pull-up resistor must be used between the TTL output-CMOS input node and Vcc. A pull-up resistor is used to avoid the floating state on the input node of the CMOS, thus using a small amount of current.
What is the propagation delay of TTL?
The standard TTL series has a typical propagation delay of 10ns (the term propagation delay was introduced in Chapter 4 and will be covered in more detail later in this chapter). By this we mean that when an input change occurs it takes 10 ns for the effect to propagate to the output.
Which logic family is characterized by multimeter transistor on the input?
| Q. | Which logic family is characterized by a multiemitter transistor on the input? |
|---|---|
| B. | cmos |
| C. | ttl |
| D. | none of the above |
| Answer» c. ttl |
Is it safe to leave unused inputs floating?
Leaving a pin configured as an input floating is dangerous simply because you cannot be sure of the state of the pin. Like you mentioned, because of your circuit, your pin was sometimes LOW or sometimes in no-man’s land or could sometimes go to HIGH.
What to do with unused pins on a microcontroller?
Connect unused input pins to pull-up or pull-down resistors. Some would claim that connecting the unused pins to ground or Vcc would be the best way to eliminate the risk of EMI interference.
Why is it not recommended to leave unused logic inputs floating what should be done to such inputs in the case of TTL and CMOS logic gates?
Do not leave them floating as then they will be in an undefined state and susceptible to external influences and can cause high current consumption or oscillation. It shouldn’t make any appreciable difference whether you tie them high or low for a standard logic gate, so long as they are tied somewhere.
What is floating logic gate?
A floating gate transistor (FGT) is a complementary metal-oxide semiconductor (CMOS) technology capable of holding an electrical charge in a memory device that is used to store data.
What is an unconnected input pin called?
One of the most basic of the faults is the infamous “floating pin” or “floating input” that can affect the I/O pins of digital integrated circuits.By not being connect to a source, Vcc, or GND, the I/O pin is susceptible to electrical noise that makes the I/O randomly fluctuate between low and high.
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