Abstract: An FM receiver having a gate circuit extracting a pilot signal contained in a stereo composite signal and a circuit driving a liquid crystal display device with the output signal from the gate circuit, in which when there exists the pilot signal, "STEREO" is displayed on the liquid crystal display device, while when there exists no pilot signal "MONO" (monoral) is displayed on the same liquid crystal display device.

Abstract: In a power supply circuit of the type including a first rectifier to be connected to an AC power source through a power switch, a transformer with primary and secondary windings, a second rectifier connected to the secondary winding of the transformer to provide a desired DC output voltage, a pulse width modulated signal producing circuit, and a transistor connected to the primary winding of the transformer to be supplied with the pulse width modulated signal so as to chop the direct current flowing through the transformer; there is further provided an oscillation circuit connected to the primary winding of the transformer for generating an oscillation signal for a predetermined period following closing of the power switch, and a third rectifier for producing a DC voltage in response to such oscillation signal, with the DC voltage from the third rectifier being supplied to the pulse width modulated signal producing circuit as an operating voltage therefor.

Abstract: An AM receiver comprises an intermediate frequency amplifying stage and a detector stage. The intermediate frequency amplifying stage includes an automatic gain controlled amplifier which functions as a positive feed back amplifier when received signals are under a predetermined level, and functions as a negative feed back amplifier when received signals are over the predetermined level.

Abstract: A differential amplifier includes differentially connected transistors, a first current mirror circuit used as an active load of the differentially connected transistors, and a second current mirror circuit connected to the common emitter side of the differentially connected transistors so as to reduce an off-set DC current that may be produced at the output terminal of the differentially connected transistors.

Abstract: A circuit adapted to detect an angle-modulated signal including a pair of terminals to which the angle-modulated signal is supplied in push-pull relation and a high-pass filter circuit coupled to the pair of terminals for transmitting those frequencies of the angle-modulated signal which exceed a cut-off frequency. A differential amplifier has a pair of inputs coupled to the high-pass filter circuit to receive the filtered angle-modulated signal as a reference signal and a quadrature generator is coupled to the high-pass filter circuit and is responsive to the filtered reference signal for generating a quadrature signal whose phase varies with respect to the reference signal as a function of the change in frequency of the reference signal.

Abstract: A circuit for demodulating a composite stereo signal of the type including a main-channel (L+R) signal and a sub-channel (L-R) signal to derive therefrom individual channel information signals L and R, respectively. A switching circuit of the balanced-modulator type is supplied with the composite stereo signal at one set of input terminals and with a switching signal whose frequency is equal to the sub-carrier onto which the sub-channel (L-R) signal is modulated, at another set of input terminals. The switching circuit produces oppositely-phased sub-channel signals which are applied to first and second current generators, respectively. An amplifier is supplied with the composite stereo signal to amplify the main-channel (L+R) signal, the amplifier including a channel separation control to adjustably vary the currents flowing through the amplifier so as to correspondingly vary the main-channel (L+R) currents.

Abstract: A signal transfer circuit suitable for a monolithic integrated circuit is operable to transfer only a desired DC biasing voltage and AC signal component from an FM discriminator output to a multiplex stereo demodulator circuit or the like at its rear stage, with a DC component contained in the FM discriminator output being cancelled and hence not transferred. The signal transfer circuit is composed of a parallel connection of a first loop including a first FM discriminating signal source and a first resistor connected in series to each other, and a second loop consisting of a second FM discriminating signal source providing an output signal which is of the same level but of reverse phase in respect to the output signal of the first discriminating signal source, second and third resistors connected in series to the second signal source, and an AC signal by-pass capacitor connected between a connection point between the second and third resistors and a reference point.

Abstract: A receiver has a first input circuit and a first amplifier connected to a first rectifier circuit and has a second input circuit and a second amplifier connected to a second rectifier circuit. The first and second rectifier circuits produce first and second direct current signals, and the first and second rectifier circuits are connected to a meter drive circuit which produces a direct current signal in response to the first or second direct current signal so that the direct current signal from the meter drive circuit actuates a meter to indicate the input level of either the first input circuit or second input circuit.

Abstract: A frequency converter of the type having a local oscillating stage for producing a local oscillating signal and a double-balanced type mixing stage provided with a first pair of inputs for receiving a signal to be frequency converted and a second pair of inputs for receiving the local oscillating signal. The output of the mixing stage can be connected through a tuned circuit so as to frequency convert the input signal to an intermediate frequency (IF) signal. The local oscillating stage includes a first pair of differentially-connected transistors, the collector electrode of one being connected to a resonant circuit and, additionally, through an RC positive feedback circuit to the base electrode of the other transistor. The double-balanced type mixing stage includes a second pair of differentially-connected transistors, one of which being connected in cascade with a first differential amplifier and the other of which being connected in cascade with a second differential amplifier.

Abstract: A balanced synchronous detector circuit for detecting the amplitude of a received signal and for detecting the phase difference between the received signal and a generated signal. A preferred application of this balanced synchronous detector circuit is in a stereo decoder of the type used for receiving and decoding a composite stereo signal. The balanced synchronous detector circuit includes a first double-balanced modulator having a first section provided with a first set of input terminals to which the received signal is applied and a second section provided with a second set of input terminals to which the locally generated signal is applied. The balanced synchronous detector circuit further includes a second double-balanced modulator having a first section formed of a portion of the second section of the first double-balanced modulator and a second section provided with a set of input terminals to which another locally generated signal is applied.

Abstract: A frequency converter utilizing a novel four terminal semiconductor device having an emitter grounded current amplification characteristic which is V-shaped wherein the gate terminal of the four terminal device is biased to the low point of the emitter grounded current amplification characteristic and wherein a signal which varies in time is applied to the gate terminal to cause the emitter grounded current amplification factor to fluctuate at both sides of its low point. A tuning circuit is provided in series with the emitter-collector terminals of the four terminal device and is tuned to twice the frequency of the input signal applied to the gate terminal.

Abstract: An FM discriminator with AFC signal producing circuits is disclosed having a pair of differential switching circuits which form the discriminator and produce output signals opposite in phase. A first constant current signal source is provided which is connected to the output terminal of one of the switching circuits. A second constant current signal source is connected to the output terminal of the other switching circuit. A biasing circuit is provided for supplying a bias to the first and second constant current signal sources respectively through a resistor. Finally, a circuit is provided for deriving AFC signals opposite in polarity from the first and second constant current signal sources, respectively.

Abstract: A stereophonic signal demodulator includes a frequency discriminator which produces a pair of composite stereo signals in response to an FM stereophonic signal applied thereto, the pair of composite stereo signals having opposite polarities to each other. A pair of stereo demodulators is supplied with at least one of the pair of composite stereo signals to produce left and right channel audio signals therefrom, respectively. The other of the pair of composite stereo signals is reduced in amplitude and is supplied to a pair of adders whereat it is correspondingly summed with the respective left and right channel audio signals to eliminate crosstalk components contained therein. In one embodiment, the reduced amplitude composite stereo signal is supplied to the respective adders by a further pair of stereo demodulators. One example of a stereo demodulator comprises a switching-type demodulator having a carrier leak suppression effect.

Abstract: A detecting circuit with improved linearity of operation for small signal voltages. A rectifying transistor has switching means connected between its collector and base to be conductive when a signal voltage of one polarity is applied to the input circuit of the transistor and nonconductive when a signal voltage of the opposite polarity is applied. The rectified signal can be obtained from either the collector or emitter of the transistor.