The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 01, 1998
Filed:
May. 21, 1997
Wolfgang Mann, Isernhagen, DE;
Horst Schaefer, Barsinghausen, DE;
Sennheiser electronic GmbH & Co. KG, Wedemark, DE;
Abstract
An oscillator circuit is provided for stabilizing the amplitude of a HF oscillation of an audio signal. In such an oscillator circuit, an audio signal having a frequency in the range of 20 Hz . . . 20 kHz is coupled into the oscillator circuit, is modulated with a high frequency and is emitted in the form of an RF audio signal having a frequency of more than 2 MHz. Such an oscillator circuit is used for instance in an infrared transmitting unit, wherein a low frequency audio signal is transformed into a higher frequency infrared signal. The higher frequency audio signals are transmitted via infrared channel to an appropriate receiving unit--for instance to infrared head phones--which comprises a receiving unit having an appropriate demodulator and preferably also a stereo-decoder in order to reproduce the low frequency audio signals. The oscillator for stabilizing the amplitude of a high frequency oscillation comprises a resonant circuit which is coupled with a first transistor having a base terminal, an emitter contact, and a collector contact. The first transistor develops an output voltage at the emitter contact which is fed back into a base circuit of the first transistor. The collector contact of the first transistor is coupled to a supply voltage source. The supply voltage source is coupled to the base terminal of the first transistor via a resistor. The emitter contact of the first transistor is coupled with the base terminal of a second transistor. The second transistor has a collector contact which is connected to the base terminal of the first transistor for controlling the voltage at the base terminal of the first transistor.