This tool computes the rise time of a signal from its bandwidth.
Trise = 0.35 / BW
- Trise is the Rise Time in Nanoseconds (ns)
- BW is the Bandwidth in Gigahertz (GHz)
As the bandwidth of the signal increases the rise time of the signal decreases. The rise time is defined as the 10-90% rise time of a square wave.
What is the rise time of a 50 MHz sine wave?
The calculator is used to find Trise = 0.35 / 0.05 = 7 nanoseconds.
What is the rise time of a 50 MHz square wave?
The bandwidth of a 50 MHz square wave for practical applications is calculated as 5×50 = 250 MHz. Trise = 0.35 / 0.25 = 1.4 nanoseconds.
In theory a square wave has an infinite number of harmonics. The amplitude of harmonics decreases as the frequency increases. For practical purposes, considering the first five harmonics is adequate.
 Bandwidth of a signal from its rise time: Rule of Thumb #1. In this post the author derives the relationship between rise time and bandwidth empirically.
 How do I determine what bandwidth of scope I require for my application? An application note that estimates a 2% measurement error when the five times rule is used.