Abstract: A rectifier system for rectifying small amplitude alternating voltage signals has a first amplifier and a control amplifier. The alternating voltage signals are supplied to the first amplifier which has its operating point set between linear operation and cut-off to achieve rectifying operation. The operating point of the first amplifier is established by a control amplifier which supplies a control voltage for setting the operating point of the first amplifier. The first amplifier and control amplifier each have a transistor arranged in the same fundamental circuit and each of which are connected to the same supply voltage. The transistor in the control amplifier, however, has an amplification which is large in comparison with the amplification of the transistor in the first amplifier. The operating point of the first amplifier is stablized by the control amplifier despite fluctuations in the supply voltage or the temperature to which both amplifiers are exposed.

Abstract: A circuit arrangement for recognizing zero transitions of signals includes a zero transition detector which receives the signals and an amplitude evaluator. The zero transition detector produces rectangular pulses which are assigned to the zero transition of the signals and the amplitude evaluator produces amplitude signals which, at least until the occurrence of the next zero transition, indicate that the amplitude of the signals was, prior to this particular zero transition, greater than the amount of a given threshold voltage. A switching stage is provided which is supplied with the rectangular signals and with the amplitude signals and which emits further signals at its output when the rectangular signals and the amplitude signals are present.