Abstract: A circuit arrangement for decoding a frequency-modulated stereo radio signal includes a FM demodulator followed by a stereo decoder and a matrix. In the matrix, by sum and difference formation, two reproduction signals are formed from a sum signal component of the output signal of the FM demodulator and from a difference signal component which has been converted from an auxiliary carrier frequency state into the audio frequency state by a synchronous demodulator. The stereo decoder is preceded by a correcting amplifier which comprises an operational amplifier having the highest possible amplification and possessing a non-inverting input and an inverting input. The output of the amplifier is fed back by way of a RC element to the inverting input so that a linear frequency response of the sum signal component and the difference signal component is formed.

Abstract: An arrangement for regulating the amplitude of a sawtooth generator employs a capacitor which is periodically charged and discharged by a current source by way of a switch, the switch being controlled by a synchronizing signal. The regulating circuit is provided with a second capacitor across which the mean value of the sawtooth pulses present across the first capacitor is formed. The regulating circuit also contains a comparator which compares the mean value with a reference value, and in dependence upon this comparison, the charging current for the first capacitor is controlled in such a manner that the mean value is equal to the reference value.

Abstract: A sum signal and a difference signal of two reproduction signals, in addition to a pilot tone, are obtained from a received signal in a circuit arrangement for a stereo-hunting device in a stereo decoder. The sum and difference signals are converted by way of a matrix operating with sum and difference formation to form the reproduction signals. In the case of a mono-received signal only the sum signal is present. The sum signal channel has connected therein an attenuator which has a control input for receiving a control voltage and in the absence of the pilot tone the control voltage causes the sum signal channel to become blocked.

Abstract: A circuit arrangement for a continuous adjustment of the base width in a stereo decoder in which a sum signal and a difference signal of two reproduction signals are obtained from a received signal and are converted by way of a matrix operating with sum and difference formation to form the reproduction signals, provides that the matrix input for the different signal is preceded by an attenuator which has a control input for receiving a control voltage and attenuates the difference signal in dependence upon the control voltage. The control voltage is dependent upon the strength of the received signal so that the difference signal component in the reproduction signals is reduced with decreasing strength of the received signal.