Abstract: A mixer circuit which is improved in distortion characteristic and band characteristic and can assure impedance matching with another circuit at a preceding stage readily and besides can prevent abnormal oscillations. The mixer circuit comprises a differential amplifier constituted from a pair of transistors grounded at the emitters thereof, and a double balanced mixer constituted from first and second pairs of transistors. A first impedance element is interposed between a junction between the emitters of the first pair of transistors of the double balanced mixer and the collector of one of the pair of transistors of the differential amplifier, and a second impedance element is interposed between a junction between the emitters of the second pair of transistors of the double balanced mixer and the collector of the other of the pair of transistors of the differential amplifier.

Abstract: A tuning apparatus is disclosed in which a television signal of either the UHF band or the VHF band is subjected to frequency conversion to obtain an intermediate frequency and, thereby, the television signal for a desired channel is selected. The tuning apparatus allows either the television signal of the UHF band or the television signal of the VHF band to be converted to an intermediate frequency by means of a common mixer. The mixer is constituted of a balanced mixer of a two-pair differential type. The tuning apparatus includes a local oscillator for reception of the UHF band and a local oscillator for reception of the VHF band. The intermediate frequency stage as the output of the mixer is provided with an attenuator of which the degree of attenuation when the UHF band is received and that when the VHF band is received are different and, thereby, the gains of the apparatus as a whole are equal when receiving the UHF band and when receiving the VHF band.

Abstract: A two-stage differential amplifier connected in cascade according to the present invention is suitable for fabrication within an integrated circuit, in which a constant current source circuit is connected with the common emitters of the transistors in the preceding stage differential amplifier, and the emitters of the transistors in the succeeding stage differential amplifier are connected with the collectors of these transistors through impedance elements. Current consumption in the overall amplifier is reduced and heat production therein is suppressed. Furthermore, since a capacitor is connected between the collector of each of the transistors in the preceding stage differential amplifier and the base of each of the transistors in the succeeding stage differential amplifier, it is possible to match easily the input and the output impedances in the succeeding and preceding amplifier by means of this capacitor and the impedance elements described above.

Abstract: A high-frequency circuit device composed of hybrid ICs, comprises an insulated substrate, an active component fabricated on the insulated substrate and including a ground terminal for grounding high-frequency signal components, a first electrode fabricated on one surface of the insulated substrate and connected to the ground terminal, a ground conductor on the insulated substrate, an annular dielectric body placed on the ground conductor, a second electrode fabricated on an opposite surface of the insulated substrate in confronting relation to the ground conductor across the dielectric body and connected to the first electrode through a through hole defined in the insulated substrate, the ground terminal of the active component connected to ground high-frequency signal components through the first electrode, the through hole, the electrode, the dielectric body, and the ground conductor.

Abstract: An amplifier for use with a local oscillator in a frequency converter including a mixer for converting a number of channel frequencies received into a certain band of intermediate frequencies, comprises a circuit for amplifying an oscillation signal from the local oscillator and supplying an amplified signal to the mixer through an output terminal thereof, and a trap circuit composed of distributed constant elements for suppressing the certain range of intermediate frequencies. The distributed constant elements include a first microstrip line connected in series to the output terminal, a second microstrip line connected in series with the first microstrip line, and a third microstrip line connected in parallel to the second microstrip line. The second microstrip line serves as an open stub, and the third microstrip line as a short stub.

Abstract: A local oscillator circuit includes an inner conductor to which a pick up coil is inductively coupled. The pickup coil is further connected with a capacitor to form a resonance circuit. The resonance frequency of the resonance circuit is set higher than those frequencies in the frequency band of the local oscillator so as to pick up oscillation signals into steady level over the frequency band.

Abstract: A buffer amplifier circuit of a wideband tuner has an output transistor. The output terminal of this transistor is grounded through a matching transformer having two taps. One of the taps constitutes a terminal through which the output signal is delivered to a mixer circuit, while the other tap is grounded through a capacitor which constitutes, in cooperation with the matching transformer, a trap circuit. This trap circuit is adapted to trap a frequency which is about twice as high as the low region oscillation frequency of a local oscillator which produces an input to the buffer amplifier circuit.

Abstract: In a Foster-Seeley discriminator circuit having a discriminating resonance circuit, resonance circuits having series resonance characteristics are respectively connected between a signal source and both ends of the discriminating resonance circuit so as to raise the level of a composite output voltage of the frequency discriminator circuit, whereby the sensitivity of the output voltage versus the frequency can be enhanced.