Pere Palà Schönwälder

Simple nonlinear large signal MOSFET model parameter extraction for class E amplifiers

In the theoretical design of high-efficiency class E amplifiers the transistor is considered as a switching device. Including the devices non-linear output capacitance and transistors internal losses as part of the design better predicts the actual performance of the amplifier. This paper presents a new parameter extraction method to obtain a simple high frequency large signal nonlinear MOS output port model from more sophisticated simulation models. The model parameters are obtained using a novel optimization technique specifically suited for non-linear switching applications. The model parameters are validated using a class E amplifier designed with an enhanced procedure that accounts for the non-linearity of the capacitance.

A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits

We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear elements. With the discretization of the equations that describe the circuit in the time domain, we obtain a nonlinear algebraic formulation where the unknowns to determine are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification in the analysis method, the stability of the solution can be computed a posteriori constructing an implicit map, where the last sample is viewed as a function of the previous samples. The application of this technique to the time-delayed Chuas circuit (TDCC) allows us to investigate the stability of the periodic solutions and to locate the period-doubling bifurcations.We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear elements. With the discretization of the equations that describe the circuit in the time domain, we obtain a nonlinear algebraic formulation where the unknowns to determine are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification in the analysis method, the stability of the solution can be computed a posteriori constructing an implicit map, where the last sample is viewed as a function of the previous samples. The application of this technique to the time-delayed Chuas circuit (TDCC) allows us to investigate the stability of the periodic solutions and to locate the period-doubling bifurcations.

A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits

The problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.<<ETX>>

CiOpt: a program for optimization of the frequency response of linear circuits

An interactive personal-computer program for optimizing the frequency response of linear lumped circuits (CiOpt) is presented. CiOpt has proved to be an efficient tool in improving designs where the inclusion of more accurate device models distorts the desired frequency response, as well as in device modeling. The outputs of CiOpt are the element values which best match the obtained and the desired frequency response. The optimization algorithms used (the Fletcher-Powell and Newtons methods, which, respectively, make use of approximate and exact second-order sensitivities) are fully described in DFD form. Analysis is carried out by obtaining the symbolic form of the transfer function H(s). An application example is presented.<<ETX>>

Steady state analysis of class-E amplifier with non-linear capacitor by means of discrete-time techniques

A new method to determine the steady state response of switched nonlinear circuits is proposed. The method is based on a Gear discretization of the circuit equations. Additional samples of the waveform are used to describe the circuit when switching from one topology to another. Results are presented for a class-E resonant inverter.