Additional Information on Op-Amp SpecificationsAdditional Op Amp specificationsComputation of Gain Bandwidth ProductFrequency Response for an Op AmpBandwidth Graphically3/1/2003 BAE 5413 1 of 5Additional Information on Op-Amp Specifications3/1/2003 BAE 5413 2 of 5Additional Op Amp specifications•Input Offset voltage – The apparent voltage offset at the input of the amplifier measured by determining the amp output (and dividing that output by the gain to calculate the input) when the differential input is shorted. (See the data sheet on the amp.)•Common mode rejection ratio (CMRR)–Common mode is the average voltage of the two inputs on a differential amplifier.–Differential voltage is the voltage difference between the two inputs on a differential amplifier–Common mode rejection ratio is the ratio of the output of the amp subjected to a common voltage to the output of the amp subjected to the same level of differential input voltage. This would be zero in an ideal amplifier.3/1/2003 BAE 5413 3 of 5•Bandwidth – normally specified in terms of Gain – Bandwidth product (GBP). The amplifier behaves like a first order filter where the corner frequency is:•The transfer function for an Op Amp may be written as:Computation of Gain Bandwidth Product1)(0sAAsGGainGBPc3/1/2003 BAE 5413 4 of 5Frequency Response for an Op Amp•Substituting j for s and computing the non-transient response:•Corner frequency occurs where the term under the root becomes significant with respect to the 1/A2 term202200000111111)(AjAAAjAjAjAjAAjG20222022111)(AAAjG20221cAGBPAc0013/1/2003 BAE 5413 5 of 5Bandwidth
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