Math interpretation

Thread Starter

Distort10n

Joined Dec 25, 2006
429
I need a quick interpretation on a particular phrase. I am putting together a lenghty document on common-mode rejection for op-amps, and I am stuck on the wording on Jiri Dostal's amplifier book.

Common-mode gain should be 0 in an ideal amplifier. With the inputs shorted to Vcm there should be no change in output voltage with any given change for Vcm.

The part I am getting stuck on is the wording. "Since the gain A and the rejection ratio X are usually of hte same order with well-designed operational amplifiers, the common-mode gain Acm is usually on the order of 1."

What does "order of 1" imply in Math Speak?

See attached for scans of this section.
 

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Thread Starter

Distort10n

Joined Dec 25, 2006
429
Well, 0dB would imply a gain of 1 or unity. Looking at figure 2-11c in the PDF the output voltage would be 0, so Acm would be 0 (ideally) when we ignore offset etc. To me, this is not 0dB or "an order of 1." Any number raised to the 0 power is 1 or unity. A 0 value is not unity.
 
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