One-Sided and Two-Sided Specs

Posted: Thu Dec 01, 2025 1:17 am Post subject: One-Sided and Two-Sided Specs

Hello Semicon Far East

I found your table on

http://www.semiconfareast.com/cpkppm.htm

very useful for some process validation I am doing.

However on your PPM values I do not understand the term one-sided specification or two-sided specification. Can you help and explain to me please ?

Regards

Joined: 20 Jun 2026 Posts: 76

One-sided specification basically means you only specify either a lower or a upper spec limit for the parameter. Two-sided specification means that the parameter needs to stay within both a lower and an upper spec spec limit.

Example of one-sided specs:

1) the upper spec limit for electrical noise, since electrical noise doesn't have a lower spec limit (the less noise the better)
2) the upper spec limit for particle count in a cleanroom (the less particles the better)
3) the lower spec limit for CMRR of an amplifier (the higher the CMRR the better)

Example of two-sided spec: an impedance of 4 ohms minimum and 8 ohms maximum (in this case, it would be bad to have an impedance that is less than 4 ohms or higher than 8 ohms)