A novel sinusoidal oscillator is presented which employs only one operational amplifier, two capacitors, and six resistors and has the facility of independent control of oscillation frequency through a single grounded resistor. The circuit may also be used as a very-low-frequency oscillator and as an economical voltage-controlled oscillator.

New canonic sinusoidal oscillator with independent frequency control through a single grounded resistor

It is assumed that a sinusoidal RC oscillator consists of a linear, passive or active RC network and an amplifier. The properties of such an oscillator are primarily dependent on its open-loop voltage transfer function. A general form of this function is introduced for RC oscillators of the second order, and expressions for the required maintenance gain and the oscillation frequency are derived. It is shown that there exist four distinct types of 2nd-order oscillators. A set of basic building elements for the oscillators is proposed. This consists of some simple RC networks, a voltage divider, a buffer and two amplifiers. The theory and the building elements are used to develop 18 novel oscillator circuits. All these oscillators have either two earthed tuning capacitances or two earthed resistances. It is shown that six of them can be tuned by varying only one capacitance or resistance. Eight of the oscillators are tunable by varying a voltage parameter; in four of these, the voltage-tuning range can be very wide. 14 additional 2nd-order oscillators are suggested. A general 3rd-order RC oscillator is also considered, and it is shown that there exist 15 distinct kinds of this oscillator. The procedure used in the development of the 2nd-order oscillators can also be applied to the design of those of the third order. It is thought that this will lead to a very large number of different oscillator circuits.

An abundance of sinusoidal RC oscillators

A novel technique to generate spectrally pure sinusoidal signals is proposed The technique provides a dramatic improvement in spectral performance compared to the existing state of the art With the proposed approach, spectral performance is inherently robust to variation in operating frequency and spectral characterization is programmable over frequencies A circuit using extremely low cost operational amplifiers and 5 % accurate passive components has been built that can generate a sine wave with THD of lesser than −100dB at frequency, f=2737 KHz 

Sinusoidal signal generation for production testing and BIST applications

A new generalized approach to the study of the variable frequency sine-wave oscillators in active RC filters having a single-element control facility is presented. The constraints on the filter functions which are amenable for generation of such oscillations with feedback are derived and a number of exemplary circuits are given and also their frequency and gain limits in tables. The oscillation stability is also studied following Loeb's criterion of limit cycle stability for systems having saturation characteristics in the active parts. The circuits are also shown to yield VCO's with voltage controlled FET as the frequency controlling parameter, The possible configurations of the amplifier circuits with operational amplifiers as the building block are considered including a discussion on bandwidth limitation.

Some observations on single-element control sine-wave oscillators

This paper presents a simple active-R voltage-controlled sinusoidal oscillator circuit which is attractive from the viewpoint of monolithic form of construction. The circuit does not require external capacitors; instead it uses the single-pole roll-off characteristics of the operational amplifier. The oscillation frequency is continuously tunable over a wide range by a single grounded resistor, and is inherently free from the condition of sustained oscillation. The circuit is suitable for IC construction, and does not suffer from the practical limitations encountered in the circuits reported previously. Experimental results agree closely with the theoretical calculations.

Operational amplifier-based voltage-controlled oscillator

A closed-loop oscillatory system, comprising an RC differentiator, a new type of an RC network and two transactors in cascade is described. For certain system conditions the circuit produces a sine wave oscillation whoso frequency is varied over a wide range from a very low to a high value. The main feature of the system is that the generation of a very low frequency oscillation is possible without incorporating a large value of the RC product. The frequency relation is derived and the results are presented in graphs.

D. Patranabis

Papers

A sine wave oscillator