P. Bowron

Noise analysis of continuous-time active filters

A rigorous and flexible direct-referral procedure for analyzing the noise performance of analog active networks is proposed. Based on an equivalent noise block diagram, it allows consistent comparisons of noise levels in active-RC, active-R, and OTA-C configurations. In each case, the measured results agree closely with theory. The state-variable operational-amplifier circuit appears to offer the best dynamic range.<<ETX>>

Noise-flow-graph analysis of OTA-C filters

Canonical and noncanonical second-order OTA-C filter circuits are analysed by means of noise flow graphs, leading to generalisation of configurations. The noise performances of specific cases are compared theoretically and experimentally. For high-Q circuits, the number of active devices is shown not to determine the output noise.

Complete dynamic range for second-order analogue active filters

Analyzing both the output noise and the large-signal harmonic distortion allows the total dynamic range of active filters to be predicted. This leads to optimization and comparison of single and multiple-amplifier RC and OTA-C second-order bandpass filter circuits. The results presented enable recommendations to be made for the choice of filter circuit in a specific signal-handling application.<<ETX>>

Nonlinear performance of composite-amplifier filters

The large-signal characteristics of some composite-amplifier filter structures using two operational amplifiers are analyzed in terms of describing functions. Conditions for linearization are developed for both inverting and noninverting configurations. Second-order nonlinear effects are minimized and overdriven nonlinear oscillations formulated. It is concluded that the price paid for introducing composite amplifiers in active filters is to increase the susceptibility to nonlinear oscillation without improving the dynamic range.<<ETX>>

Output noise of generalized high-order allpole OTA-C filters

High-order transconductor-capacitor filter structures are analysed by means of noise flow graphs. Their noise performance is generalised and compared for different low-pass approximation designs. Contrary to the known property of active RC networks, the IFLF configuration only exhibits optimal noise suppression well within the passband and not at the filter critical frequency.

Dynamic-range comparison of second-order active-RC and OTA-C filters

Analysis of both the output noise and the large-signal harmonic distortion in terms of block diagrams allows the total dynamic range of active filters to be predicted theoretically. This leads to optimisation and comparison of single and multiple-amplifier RC and OTA-C second-order bandpass filter circuits.

HD and IMD prediction techniques for active filters

Two single-domain techniques for evaluating the output distortion of nonlinear systems are described as a means of circumventing the time-frequency transformations of standard methods. These are compared with respect to accuracy, computational efficiency and flexibility for a bandpass active filter containing a saturation-type nonlinearity.<<ETX>>

Analogue active filters with two-tone large-signal excitation

Block-diagram representation together with harmonic-balance analysis enables evaluation of intermodulation entirely in the time domain, with consequent computational economy. The output distortions of various active-filter circuits are then compared.<<ETX>>

Evaluation of the large-signal behaviour of active filters

A describing function representation of the saturation nonlinearity of operational amplifiers is used to formulate the nonlinear transfer functions of multiple-amplifier filters. The efficacy of various functional approximations for shortening computer time is assessed. Computationally efficient means of predicting jump resonance and nonlinear oscillations are presented, based on the representation.<<ETX>>