I've saying this without referring to a possible relation to comparator toggle rates. Just meaning, that the application mostly needs either a fast comparator reaction, or even more important, a reaction with predictable delay. The latter point addresses delay skew and signal dependant delay.Tpd should be considerably below signal cycle time. But by how much?
How does a comparator prop delay relate to its speed(Bandwidth).
I googled but could not find any useful material.
Prop delay is just the delay from input to output. It doesn't say anything about max frequency input or Bandwidth of the comparator.
If you think of the comparator as an op amp with high gain, the gain should roll off at some frequency. I can't find any gain Vs. freq plots in the datasheets.
Hi All, Sorry it may be too late to reply, but I felt the thread was still incomplete.
It will be beneficial if I elaborate more to make meaningful thread.
So from opamp (comparator) ft = UGB = f3-db*Adc ( where f3-db: 3dB bandwidth, Adc = DC gain of OPAMP)
Time constant of comparator = 1/(2*PI*f3-db). If we assume Comparator as a first order RC delay, it will take around 6 time constant to settle to final value.
Thats why Prop. Delay = 6* Time constant = 1/f3-db = UGB/Adc.
ft = UGB = f3-db*Adc
Thanks for explaining your calculation. Obviously the result doesn't apply to MAX9144 which has 40 ns propagation delay, as reported below. I guess, you'll observe a similar mismatch for other standard comparators.For single pole system, f3-db refers to first pole frequency.
For 60dB DC gain opamp, with 200MHz UGB, first pole is at 200MHz/1000 = 200KHz.
That gives Prop. Delay = 1/200KHz = 5us.
Hi FVM, Good Morning,I basically agree to leo_o2, that there's no direct relation between small signal bandwidth and propagatiopn delay.
I agree as f3-db≈1/6RC.Time constant of comparator = 1/(2*PI*f3-db). If we assume Comparator as a first order RC delay, it will take around 6 time constant to settle to final value.
It is not about propogation delay, it is about rise/fall time.Thats why Prop. Delay = 6* Time constant = 1/f3-db.
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