Oscillators – Solid state active element oscillator – Transistors
Patent
1997-04-25
1998-12-22
Kinkead, Arnold
Oscillators
Solid state active element oscillator
Transistors
331143, 331177R, 331175, H03K 3023, H03K 300
Patent
active
058523871
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement, of a controllable oscillator. A circuit arrangement of this type is disclosed, for example, in The Macrochip, Design Manual, 1987, Feranti Interdesign, Inc. Scotts Valley, Calif., page 1. However, this circuit arrangement has the disadvantage of increasing inaccuracy between a frequency-setting adjusting variable and an expected oscillator frequency, in particular at low and high frequencies.
SUMMARY OF THE INVENTION
The object of the invention is to design a voltage-controlled oscillator in such a way that it is suitable for a large frequency range.
In general terms the present invention is a controllable oscillator having a comparator unit for comparing the voltage potential, fed to its signal inputs, of a storage element with first and second reference voltage potentials. A control stage which is connected to the comparison unit and, under the control of the latter, defines a charging and discharge cycle via a switching unit. Two current mirror units, designed as controlled current sources, charge and discharge the storage element. An adjusting current is fed in via an input of the first current mirror unit, a first output being connected to the storage element and a second output being connected to an input of the second current mirror unit. As a result the oscillator frequency is controlled by the adjusting current via the first and second current mirror units. An impedance converter is provided whose input is connected to the storage unit and whose output is connected to the signal input of the comparison unit. The second output of the first current mirror unit is connected directly to the input of the second current mirror unit, the first output of which is connected to the storage element via the switching unit and the second output of which is likewise connected to the signal input of the comparison unit. The emitter of the impedance converter is connected to a current source whose output current is proportional to the adjusting current.
Advantageous developments of the present invention are as follows.
The current mirror unit has at least two transistors, which are interconnected by their base terminals, and one diode connected to there terminals.
The comparison unit is a window comparator formed from first and second comparators.
An impedance converter is provided, at whose input a first reference voltage potential is present and whose output is connected to a reference voltage input of the first comparator. A second impedance converter is provided, at whose input a second reference voltage potential is present and whose output is connected to a reference voltage input of the second comparator. The second controllable current source has two further outputs, which are respectively connected to an output of the first and second impedance converters.
The control stage provided has a bistable multivibrator which is controlled by the output signals of the window comparator.
A level adapting unit is provided, via which the output signal of the bistable multivibrator is fed to the switching unit.
A current subtraction unit is provided, to which a constant maximum current and at least one control current are fed and which outputs the adjusting current at its output.
The invention has the advantage that the currents influencing the oscillator frequency are used exclusively to charge and discharge the storage unit of the oscillator and the oscillator is particularly suitable for producing very large and extremely small repetition rates.
A further advantage of the circuit arrangement is that with a reduction in the repetition rate, the current consumption of the circuit arrangement specified decreases and a favorable efficiency is produced in conjunction with a low power requirement.
The circuit arrangement has the further advantage that the repetition rate can be set within very wide ranges.
A further advantage of the circuit arrangement is that it can be embodied in an integrated circuit and requires very few external compone
REFERENCES:
patent: 4233575 (1980-11-01), Chapman et al.
patent: 4983931 (1991-01-01), Nakano
patent: 5418502 (1995-05-01), Ma et al.
patent: 5668508 (1997-09-01), Pulvirenti et al.
Radio Fernsehen Elektronik, vol. 38, No. 1, (1989), Horst Juengling, "Spannungsgesteuerter Funktionsgenerator IA 338 D", pp. 8-12.
The Macrochip, Design Manual, (1987), Feranti Interdesign, Inc., Scotts Valley, California, p.1.
Brakus Bogdan
Roth Heinz-Jurgen
Kinkead Arnold
SGS-Thomson Microelectronics GmbH
Siemens Aktiengesellschaft
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