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.
How is propagation delay calculated?
It can be computed as the ratio between the link length and the propagation speed over the specific medium. Propagation delay is equal to d / s where d is the distance and s is the wave propagation speed. In wireless communication, s=c, i.e. the speed of light.
What is a good propagation delay?
Propagation delay is defined as the flight time of packets over the transmission link and is limited by the speed of light. For example, if the source and destination are in the same building at the distance of 200 m, the propagation delay will be ∼ 1 μsec.
How is propagation delay improved in totem pole TTL logic?
Totem Pole Output Totem Pole means the addition of an active pull up the circuit in the output of the Gate which results in a reduction of propagation delay. Logic operation is the same as the open collector output.
Why is propagation delay important?
Inconsistent propagation delay in an IC can cause data errors or race conditions on a chip. Therefore, the propagation delay is an important factor in high-speed circuit design and is a limiting factor of the processing speed, or hertz, that a processor can run at.
Why do we use TTL?
TTL is particularly well suited to bipolar integrated circuits because additional inputs to a gate merely required additional emitters on a shared base region of the input transistor. If individually packaged transistors were used, the cost of all the transistors would discourage one from using such an input structure.
What is the propagation delay of a TTL device?
In other words, the propagation delay is like the sum of all times required to initiate the cascade of switching events in the circuit. There are some tradeoffs between power consumption and propagation delay for TTL devices. TTL propagation delay is ~33 ns or less, depending on the sub-family.
How much power does a TTL device use?
There are some tradeoffs between power consumption and propagation delay for TTL devices. TTL propagation delay is ~33 ns or less, depending on the sub-family. High-speed TTL has propagation delay reaching 6 ns, although this sub-family consumes more power than other subtypes.
What is the propagation delay of a logic gate?
Propagation Delay. What is propagation delay: Propagation delay of a logic gate is defined as the time it takes for the effect of change in input to be visible at the output. In other words, propagation delay is the time required for the input to be propagated to the output.
How much does the propagation delay increase with ECL?
The propagation delay can increase by anywhere from 100 to 200 ps for each additional switching gate. With CMOS devices, this is a drop in the bucket compared to the propagation delay for a single gate. With ECL or TTL, this represents a significant increase in propagation delay in packages with a large number of logic circuits.