Question
Download Solution PDFA given op-amp has an differential gain of 110 dB and a CMRR rating of 100 dB. What should be the open loop common mode gain of this op-amp ?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
CMRR (Common mode rejection ratio) is defined as the ratio of differential-mode voltage gain (Ad) and the common-mode voltage gain (AC).
Mathematically, in dB this is expressed as:
\(CMRR(dB)= 20\log \left| {\frac{{{A_d}}}{{{A_c}}}} \right| \)Ad = Differential gain
Ac = Common mode gain
Using the property of log, we can write:
CMRR (dB) = 20log (Ad) - 20log (Ac)
CMRR (dB) = Ad(dB) - Ac(dB)
Calculation:
Given:
Ad(dB) = 110 dB
CMRR (dB) = 100 dB
We can write:
CMRR (dB) = Ad(dB) - Ac(dB)
100 dB = 110 dB - Ac(dB)
Ac(dB) = 110 dB - 100 dB
Ac(dB) = 10 dB
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