COMPUTATION OF THE STEADY-STATE SOLUTION OF NONLINEAR CIRCUITS WITH TIME-DOMAIN AND LARGE-SIGNAL SMALL-SIGNAL ANALYSIS-METHODS

This work presents two steady-state methods for nonlinear circuits. Th e first method is a steady-state time-domain analysis method. The meth od is based on integration over the period of the circuit; the first a nd last voltages (currents) in the period are required to be equal. Th ree extensions to the method are presented. The first one is steady-st ate time-domain analysis with variable time step integration. The algo rithm is based on using the changes of the sources as initial data of the analysis and subsequently using the truncation error with optimiza tion. The second extension presents a steady-state time-domain analysi s including components defined in the frequency domain. The circuit is divided into time and frequency-dependent parts where the time-domain representation of the frequency-dependent part is created with the ai d of a convolution integral. The third, the steady-state time-domain a nalysis method is extended to analyze nonlinear oscillators. The oscil lator problem is solved using optimization with a test element. The op timization variables are the oscillating frequency and the currents at two time points in the feedback loop of the circuit. The second metho d is a large-signal-small-signal analysis method for nonlinear circuit s. The method can be used to calculate the steady-state time domain re presentation as well as the frequency response of switched capacitor c ircuits. The analysis is performed in three steps, where the first ste p can be taken in three different ways. The first way makes it possibl e to analyze switched capacitor circuits with finite on and off-resist ances for the switches. The other two ways make it possible to use any nonideal models for switches, i.e., all modeling levels of MOSFETs as switches including parasitic components can be simulated. The method proposed may be applied to mixer analysis for the case of a strong LO and a weak RF signal. Noise of the periodically operated nonlinear cir cuit can also be calculated. For both methods, examples are given to d emonstrate that the methods proposed are efficient and sufficiently fa st to be used in circuit design. The simulation results show good agre ement with those obtained by harmonic balance and transient analysis.