Ultra-precision PCB Fabrication, High Frequency PCB, High Speed PCB, IC Substrate, Multilayer PCB and PCB Assembly.
The most reliable PCB custom service factory.
PCB Tech

PCB Tech

PCB Tech

PCB Tech

What is High Frequency Circuit PCB?
2020-09-01
View:280
Author:Holia

What is High Frequency Circuit?


In a digital circuit, whether it is a high-frequency circuit depends on the rising and falling edges of the signal, rather than the frequency of the signal.


Formula: F2 = 1 / (TR × π), TR is the rising / falling delay time of signal.


If F2 > 100MHz, it should be considered according to the high-frequency circuit, and the following conditions must be designed according to the high-frequency rules:

  1. The system clock frequency exceeds 50MHz

  2. The device with rise / fall time less than 5 ns is used

  3. Digital / analog hybrid circuit


The rise / fall time and wiring length of logic devices limit the rise / fall time tr component F2 = 1 / Fmax = 10 * distance (microstrip) line distance (microstrip line)πTr   F2  



74HC13-15ns24MHz240MHz117cm91cm
74LS9.5ns34MHz340MHz85.5cm66.5cm
74H4-6ns80MHz800MHz35cm28cm
74S3-4ns106MHz1.1GHz27cm21cm
74HCT5-15ns64MHz640MHz45cm34cm
74ALS2-10ns160MHz1.6GHz13cm13cm
74FCT2-5ns160MHz1.6GHz13cm13cm
74F1.5ns212MHz2.1GHz12.5cm10.5cm
ECL12K 
1.5ns212MHz2.1GHz12.5cm10.5cm
ECL100K0.75ns424MHz4.2GHz6cm5cm