Abstract: In digital signal processing, it is necessary to work with system clocks. This often requires the use of different system clocks which have a corresponding accuracy. In a ring oscillator circuit having an even number of ring inverters caused to oscillate by the same number of shunt inverters, a stepwise change of the frequency is achieved by switching additional inverters. By switching between two modes, several multiples of a fundamental frequency can be adjusted. By merely switching the additional inverters, the current consumption at each adjusted frequency remains constant. This has the advantage that the frequency thus generated is very stable and, hence, corresponds to the accuracy requirements imposed on digital signal processing. Moreover, this system is operated via a current supply so that a further improvement of the accuracy and freedom from interference of the generated frequencies is achieved.

Abstract: An emitter-coupled multivibrator circuit independent of temperature and supply voltage includes an oscillator circuit (11), a current control circuit (12) and a supply voltage circuit (13) for producing at least one reference voltage. The oscillator circuit consists of two switching transistors (15,16), each with a collector coupled to a respective collector-emitter branch of two interception transistors (37,38) for a lower threshold voltage and of two interception transistors (35,36) for a higher threshold voltage and, to respective active loads (28,29) of the current control circuit (12). The loads (28,29) are associated with a current mirror branch (31) including transistors (30,34) and a current source (32,33). The bases of the interception transistors (37,38) are connected to a reference voltage U.sub.b2 and those of the interception transistors (35,36) are connected to the emitter of the transistor (34).