Oscillators – Solid state active element oscillator – Transistors
Patent
1995-05-15
1999-09-07
Grimm, Siegfried H.
Oscillators
Solid state active element oscillator
Transistors
327553, 327557, 333214, 331177R, H03B 512, H03H 1148
Patent
active
059492953
DESCRIPTION:
BRIEF SUMMARY
In IC technology, the aim is to design as far as possible all circuit components in a completely monolithically integrated fashion, in order to avoid the arrangement of external components. However, this encounters difficulties in the case of large capacitances/inductances, in particular, so that compromises or incomplete solutions are frequently accepted.
Thus, circuit concepts are known for monolithically integrated LC bandpass filters in which the necessary inductances are realized as planar spiral inductors by means of aluminum tracks on the chip. Such inductors are, however, not electrically adjustable, on the one hand, and they are only of low quality on the other hand, because of their series resistance and owing to parasitic coupling capacitances (N. M. Nguyen, R. G. Meyer: "Si IC-compatible inductors and LC passive filters", IEEE Journal of Solid-State Circuits, Vol. 25, No. 4, August 1990, pages 1028-1031; N. M. Nguyen, R. G. Meyer: "A Si bipolar monolithic RF bandpass amplifier", IEEE Journal of Solid-State Circuits, Vol. 27, No. 1, January 1992, pages 123-127).
The aim of the invention is to specify a completely monolithically integrated, electrically adjustable resonant circuit which can be used, for example, as an adjustable bandpass filter or as a resonator for a controllable oscillator and which satisfies all the requirements of high-quality IC technology. The invention achieves this aim by means of the basic concept in accordance with patent claim 1 and the development of this basic concept in accordance with patent claims 2-8.
The invention proceeds from the consideration of generating the required inductances by transformation of impedances from the base circuit into the emitter circuit of suitably connected bipolar transistors, the frequency dependence of the current gain being utilized. The inductances realized in this way on the one hand have a higher quality as an advantage with respect to the known concept and, on the other hand they can be electrically adjusted in a wide frequency range. Moreover, the geometrical dimensions of such inductors are smaller than those of the planar spiral inductors.
The utilization of the frequency dependence of the current gain of the bipolar transistors to realize inductances by transformation of impedance renders it possible to realize electrically tunable inductors by means of which the center frequency of a resonant circuit can be adjusted. As a second essential feature, the attenuation of the resonant circuit is reduced by negative resistances on the basis of the finite quality of the inductances thus generated, these negative resistances likewise being produced on the basis of impedance transformations. The change in filter capacities which is produced simultaneously with the tuning of the inductors leads to a relationship between the electrical manipulated variable and the center frequency of the resonant circuit which is approximately linear over a wide range.
The resonant circuit according to the invention can be used directly as an active single-stage or multistage bandpass filter. However, it is possible to use the resonant circuit according to the invention with particular advantage to form a completely monolithically integrated, electrically adjustable oscillator such as is required for many applications, for example in the field of telecommunications.
Various concepts are known for such oscillators and can be classified into the three groups of relaxation oscillators, ring oscillators and LC oscillators.
Relaxation oscillators (for example, M. Soyuer, J. D. Warnock: "Multigigahertz Voltage-Controlled Oscillators in Advanced Silicon Bipolar Technology", IEEE Journal of Solid-State Circuits, Vol. 27, No. 4, April 1992, pages 668-670; J. G. Sneep, C. J. M. Verhoeven: "A New Low-Noise 100-MHz Balanced Relaxation Oscillator", IEEE Journal of Solid-State Circuits, Vol. 25, No. 3, June 1990, pages 692-698; A. A. Abidi, R. G. Meyer: "Noise in Relaxation Oscillators", IEEE Journal of Solid-State Circuits, Vol. 18, No. 6, December 1983, pages 794-
REFERENCES:
patent: 3758885 (1973-09-01), Voorman et al.
patent: 4383230 (1983-05-01), Manzolini
patent: 5347238 (1994-09-01), Kobayashi
Grimm Siegfried H.
Sican, Gesellschaft Fur Silizium-Anwendungen Und Cad/Cat Nieders
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