Experimental Characterization of Operational Amplifiers: A System Identification Approach— Part II: Calibration and Measurements

R. Pintelon, Y. Rolain, G. Vandersteen, J. Schoukens
2004 IEEE Transactions on Instrumentation and Measurement  
Using specially designed broadband periodic random excitation signals, the open loop gain, and the common mode and power supply rejection ratios of operational amplifiers are measured and modeled. The proposed modeling technique 1) takes into account the measurement uncertainty and the nonlinear distortions, 2) gives information about possible unmodeled dynamics, 3) detects, quantifies, and classifies the nonlinear distortions, and 4) provides opamp parameters (time constants, gain-bandwidth
more » ... , gain-bandwidth product, etc.) with confidence bounds. The approach is suitable for the experimental characterization of operational amplifiers (see Part II) as well as the fast evaluation of new operational amplifiers designs using network simulators (see [12]). Part II handles the calibration of the experimental setup and illustrates the theory on real measurements. Index Terms-Common mode rejection, linear characteristics, nonlinear distortions, open loop gain, operational amplifier, power supply rejection, system identification. I. INTRODUCTION T WO TYPES OF measurement results are available in literature: the operational amplifier (opamp) characteristics are derived either from a small number (one, two, or three) of single sine measurements [1]-[5], or from a broadband frequency response function measurement using single sine excitations [6]-[8]. In all cases, except for [6], the calculation of the opamp parameters (poles, gain-bandwidth product, etc.) is based on low (first or second) order models. Experimental results for the open loop gain can be found in [1]-[6], for the common mode rejection ratio in [6], [7], and for the power supply rejection ratios in [6], [8] . The proposed measurement methods 1) give no information about the possible unmodeled dynamics (higher-order models may be needed to explain the opamp characteristics) and the possible nonlinear behavior of the opamp and 2) provide no confidence bounds on the estimated opamp parameters.
doi:10.1109/tim.2004.827092 fatcat:omknodkxxbcnznciaoustod664