We present a method for application of formal techniques like model checking and equivalence checking for validation of the transient response of nonlinear analog circuits. We propose a temporal logic called Ana CTL (computational tree logic for analog circuit verification) which is suitable for specifying properties specific to analog circuits. The application of Ana CTL for validation of transient behavior of arbitrarily nonlinear analog circuits is presented. The transient response of a circuit under all possible input waveforms is represented as a finite state machine (FSM), by bounding and discretizing the continuous state space of an analog circuit. We have developed algorithms to run Ana CTL queries on this discretized model using search-based methods which reduce the runtime considerably by avoiding creation of the whole FSM. The application of these methods on several real-life analog circuits is presented and we show that this system is a useful aid for detecting and debugging early design errors. We also present methods for checking the equivalence of transient response of two analog circuits. The behavior of two different analog circuits can rarely be exactly similar. Hence, we introduce a notion of approximate equivalence. A query language for checking different notions of user-definable approximate equivalence is presented which extends the syntax of the Ana CTL model checking language. In its extended form, Ana CTL can be used combining model checking with equivalence checking.
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