Op-amp Gain-bandwidth Product Research Articles

Maximum oscillation frequencies and ft sensitivities of two groups of single-VFOA active-RC oscillators

Two groups of three active-RC oscillators that use a single voltage feedback op amp (VFOA) are compared. Linear analysis using a first-order VFOA model shows that all six oscillators have the same maximum oscillation frequency (OF) of 16.67% of the op amp gain-bandwidth product (GBP), despite the fact that based on an ideal VFOA the gain required in the oscillator amplifier section is 3 for one group and 1.5 for the other.Sensitivity of OF to op amp GBP is found to be the same for both groups. Simulation results using a nonlinear VFOA macromodel give good agreement with linear analysis.

Low-voltage CMOS op-amp with rail-to-rail input and output signal swing for continuous-time signal processing using multiple-input floating-gate transistors

A scheme for low-voltage CMOS op-amp operation with rail-to-rail input and output signal swing and constant g/sub m/ is presented. Single-ended and fully differential versions are discussed. The scheme is based on the use of multiple-input floating-gate transistors and allows direct implementation of linear weighted addition of continuous-time signals. Simulations are presented that verify the scheme operating with a 1.2-V single supply, 1.2-V input and output solving, 5-MHz op-amp gain-bandwidth product, and a 192-/spl mu/W power dissipation with a 50-pF load and 300/spl times/300 /spl mu/m/sup 2/ silicon area. These results are obtained for 0.85-V transistor threshold voltages. Experimental results are shown that verify the correct functionality of the proposed approach.

Sinusoidal oscillators with slew-rate type nonlinearity

This paper is a continuation of [1] and deals with a class of single-op-amp sinusoidal oscillators working under the amplitude limiting regime of a slew-rate nonlinearity. The Wien-bridge oscillator example is chosen for a detailed analysis. It is shown, using the first-order determining equation, that the oscillation-frequency (f0) depends upon the passive elements of the oscillator structure only; it is independent of the op-amp gain-bandwidth product (Gfl)! Moreover, the oscillation-amplitude (A0) is a function of the oscillation-frequency, of the op-amp parameters: slew-rate factor (SR), and GB and finally, of the attenuation of the Wien-bridge resistive branch (k). Notable is the high sensitivity of the amplitude A0 with respect to the changes in the factor k. Furthermore, an upper bound for the realizable oscillation-frequency is developed and verified on the experimental data. Finally, the harmonic content (A) is computed for different fo's and compared with those values obtained by means of the describing-function method.

Design of switched-capacitor filters using non-ideal op amps

A general synthesis procedure is given for the realization of switched-capacitor filters in the z-domain. The method uses biphased switches, capacitors and non-ideal op amps with finite gain-bandwidth product. The design includes at the outset the effects of the op amp gain-bandwidth product. Two examples are given which have been verified by a computer program.

Finite gain - bandwidth product effects on a pair of pseudo-N-path SC filters

A detailed analysis of two novel SC pseudo- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> -path filters [3], [4] are presented to determine the effects of their transfer functions due to the op amp gain-bandwidth product (GB). To appreciate the difference between the two filters, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</tex> -plane root locus plots as a function of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GB/f_{c}</tex> are presented.

Active Compensated Bandpass Filter with Reduced Sensitivity to Op Amp Gain Bandwidth Product

Active Compensated Bandpass Filter with Reduced Sensitivity to Op Amp Gain Bandwidth Product