K. A. Stromsmoe

On the realization of highly selective networks by low Q-factor stages

This paper presents a method for interchanging a secondorder frequency emphasizing network with high Q -factor poles by a more complicated network that consists of several low Q -factor stages. The transfer function of this new network approximates in a Chebyshev manner the square modulus of a given transfer function. It is shown that all low Q -factor pairs of the poles must coincide. The procedure includes a method for determining the numerator zeros of the approximating transfer function.

Amplitude control in a twin-T bridge RC-oscillator using a window comparator

The paper describes amplitude control which is achieved by restoring, during each oscillation period, the voltage at the capacitor connected between the inner node and ground of the twin-T bridge RC-oscillator. The calculations of the amplitude transient, steady-state waveforms and total harmonic distortion are given. All calculations were experimentally verified.

An approximation of a transfer function by one with lower Q's

This article presents a method for interchanging a portion of a transfer function with high Q -factor poles by a more complicated transfer function that can be realized with lower Q -factor stages. The limit for the possible Q -factor lowering is determined by the root locus for the poles of this high Q -portion. The approximation error can be reduced in a geometric progression by increasing the number of low Q -factor stages. A method for determining the poles and zeros of the approximating function is described and an example of interchange of a bandpass filter transfer function is given.

Synthesis of integrable high-Q filters using grounded unity-gain amplifiers†

Some general procedures for synthesizing filters using only RC elements and grounded voltage and current unity-gain amplifiers (GVTJGAs and GCUGAs) are discussed. Filters are designed according to theories with respect to minimum sensitivity to parameter variations by Calahan and Horowitz,. State-variable technique is also used to yield the optimal result in terms of the number of capacitors used and the spread of clement values. Another method, a coefficient-matching technique, leads to low-sensitive results with only three active elements. Sensitivity is investigated in each case and is found to be low for high value of the quality factor in most cases, and independent of element values in some cases ; thus high Q poles of bandpass filters are realizable in practice. Filters so designed also possess the desirable property of having a common ground for both the input and output ports.