Theoretical background of oscillation-based test of biquad SC filter
U. Kač, F. Novak
Electrotechnical Review , 2007, 74(3): 92-98
This paper presents a general approach to the design of test procedures and related structures for the oscillation-based test of analog integrated filters implemented with switched-capacitor structures. A generalized theoretical approach based on the analysis of the generic discrete-time second-order transfer function is presented. Exact relations between the parameters describing the filter circuit in the continuous time domain and the coefficients of the discrete-time transfer function are derived and used to determine necessary conditions for establishing sustained oscillations in the tested circuit. Two different approaches to the transformation of the second-order SC stage into an oscillator are considered. The first technique relies on internal SC stage reconfiguration by using the existing or including additional analog switches. The second approach is based on external nonlinear feedback thus providing for better control of the operation conditions of the circuit under test.
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