Abstract: A filter circuit includes two current amplifiers and two capacitors constituted of MOS or MIS transistors. An output terminal of the first current amplifier is connected to an input terminal of the second current amplifier, while an output terminal of the second current amplifier is connected to an input terminal of the first current amplifier. One end of the first capacitor is connected to the input terminal of the first current amplifier, while one end of the second capacitor is connected to the output terminal of the first current amplifier the other end thereof is grounded. When an input signal is supplied through the first capacitor, an output signal through a band-pass filter is issued from the output terminal of the first current amplifier, and an output signal through a high-pass filter is issued from the output terminal of the second current amplifier.

Abstract: A filter circuit having a first variable resistive element determining the time constant of the filter circuit and a band pass filter having a second variable resistive element determining the time constant of the band pass filter. Each variable resistive element is connected to receive a time constant control signal which is obtained through a compensation circuit which receives an output voltage signal from a phase detection circuit for detecting a phase difference between the output signal of the band pass filter and a reference signal. The compensation circuit has a comparison circuit for comparing a first voltage generated by a third variable resistive element and a second voltage generated by a constant trimming resistor to generate the output voltage signal.

Abstract: In an automatic gain control loop circuit supplied with two channel signals alternately input thereto, a first capacitor filter and stores the first signal output from the level detector circuit, and a second capacitor filters and stores the second signal output from the level detector circuit. The second signal is output only during the signal period of a second channel included in the two channels. An adder adds the second signal stored in the second capacitor to the first signal stored in the first capacitor. A switch selects the first signal stored in the first capacitor during the signal period of the first channel, and selects an output from the adder during the signal period of the second channel. The selected signal is fed back to the gain control input terminal of the variable-gain amplifier circuit. With there features, a flicker is prevented from occurring when the two channel signals are switched.

Abstract: A luminance signal/color signal separator circuit having an input terminal and luminance and color output terminals includes a comb filter connected between the input terminal and the color output terminal; an amplitude detector having an input connected to the color output terminal; a filter having a first input connected to the input terminal and a second input connected to an output of the amplitude detector; and a combiner having an output connected to the luminance output terminal, a first input connected to the input terminal and a second input connected to an output of the filter. The separator circuit processes a composite signal which includes an original luminance signal and an original color signal. The filter passes a gain controlled color band signal.

Abstract: For realizing more accurately a signal separation of a luminance signal and a chrominance signal, a signal separation automatic adjusting circuit in a YC separation comb filter includes an amplitude adjusting loop for detecting a level of a color signal component remaining in the separated luminance signal to adjust amplitudes in an image signal and a 1H delayed image signal, a first phase adjusting loop for adjusting phases of the image signal and the 1H delayed image signal which are respectively inputted into an adder, and a second phase adjusting loop for adjusting phases of the image signal and the 1H delayed image signal in the manner of suppressing the color signal remaining in the luminance signal. According to the constitution, it is possible to prevent an intermix of the color signal component into the luminance, thereby obtaining the YC separation automatic adjusting circuit having a high accuracy.

Abstract: An automatic gain control circuit for processing a reproduced color signal in a VCR which may include first and second feedback loops respectively positioned before and after a comb filter. In the first feedback loop, the color signal is amplified by a first variable gain amplifier and supplied to both a first burst detector and the comb filter via a frequency converter and a band-pass filter. The first burst detector detects the peak level of the burst signal included in the color signal and controls the gain of the first amplifier for stabilizing the level of the burst signal. The comb filter removes cross-talk components from the color signal and supplies an output signal to the second feedback loop. In the second feedback loop, the output signal is amplified by a second variable gain amplifier and supplied to a second burst detector.

Abstract: A variable voltage to current conversion circuit having a first transistor and a second transistor having bases which are supplied with differentially related voltage, a diode-fashion third transistor having a base and a collector commonly connected to the emitter of the first transistor through a first resistor, a diode-fashion fourth transistor having a base and a collector commonly connected to the emitter of the second transistor through a second resistor, a first current source coupled to a connection node of the emitters of the third and the fourth transistors, a fifth and a sixth transistors having bases connected to the collectors of the third and the fourth transistors, respectively, and emitters commonly connected to a second current source, and a third current source coupled to the connection node of the collectors of the second and the sixth transistors.

Abstract: A low range chroma signal reproduced from a recording medium is converted in the frequency by a frequency converter to obtain an original carrier chroma signal, then the carrier chroma signal is passed through a comb filter for removing a crosstalk and is output further through a phase shifting circuit, a burst signal of the phase shifting output is compared in the phase with a reference signal, the phase comparing output is smoothed by a filter, is then fed to a controlling terminal of a variable oscillator to control the oscillating frequency and is fed to a controlling terminal of the above mentioned phase shifting circuit to control the phase shifting amount. In this formation, a sub-APC loop including no comb filter is superimposed on a conventional APC loop and a response can be made until a high frequency. A color irregularity in a high frequency range (high range phase fluctuation of a carrier chroma signal) which has not been able to be removed can be reduced.

Abstract: A periodic input signal Sa is input into a first subtracter and is input on the other hand into a second subtracter, a difference signal Sb between the periodic input signal Sa and a signal Se obtained by delaying this signal by 1H is obtained in a second subtracter. This difference signal Sb is input into a first limiter amplifier having a specific gain factor and a second limiter amplifier having a smaller gain factor, the outputs of the first and second limiter amplifiers are input into a third subtracter. A signal Sc is obtained by subtracting the output of the second limiter amplifier from the output of the first limiter amplifier. This signal Sc is subtracted from the input signal Sa by the first subtracter to obtain a filter output Sd.

Abstract: A contour accentuation circuit for color signal comprises a variable gain amplifier, an output circuit and differential circuit. The output circuit outputs the signal according to the output signal from the variable gain amplifier and outputs the constant level signal to the output signal of amplitude level over predetermined level from the amplifier. The differential circuit differentiates the output signal from the output circuit and the amplifier amplifies and accentuates the contour of the input signal under the output control signal from the differential circuit.

Abstract: A first input section inputs a first signal serving as a trigger. A second input section inputs second and third signals having phases opposite to each other to set a time period width. A first data hold section obtains a first hold output in response to the first and second signals respectively output from the first and second input sections. A second data hold section obtains a second hold output in response to the first and third signals respectively output from the first and second input sections. A determination section determines whether the first hold output from the first data hold section or the second hold output from the second data hold section is output first. A selection section selects the second or third signal from the second input section in accordance with a determination result from the determination section.

Abstract: An AFC circuit using counters, flip-flops and logic gates produces a first pulse signal only when the phase of a VCO output signal lags the phase of a reference signal, and produces a second pulse signal only when the phase of the VCO output signal leads the phase of the reference signal. The first and second pulse signals control a switch to connect a first or a second constant current source to charge or discharge a filter circuit, to thereby produce a control voltage for the VCO. When the VCO output signal is in phase with the reference signal, the switch remains in a neutral position to hold a constant control voltage on the filter.

Abstract: An automatic adjustment circuit for adjusting the time constant of a filter circuit. The adjustment circuit includes a source of reference frequency signal, an oscillator for generating an oscillation signal, and a detector for detecting the difference in one of phase and frequency between the reference frequency signal and the oscillation signal and generating a control signal for automatically adjusting the time constant of the filter circuit.

Abstract: An oscillation circuit for an integrated circuit device. The oscillation circuit includes a band-pass filter for producing an output signal having a voltage and a defined resonance frequency and a voltage to current converter type limiter amplifier connected to the band-pass filter for supplying a current to the band-pass filter corresponding to the voltage of the output signal of the band-pass filter.

Abstract: An automatic phase control (APC) circuit with improved reliability of phase control, in which a phase of a reference signal from a crystal oscillator is alternately switched between two phases by a switch. The APC circuit includes a phase locked loop (PLL) for stabilizing a phase of a signal, e.g., a playback color signal of a VTR, with the phase of the reference signal, which is changed alternnately in phase between the two phases. An irregular detection (ID) circuit monitors the irregularity of the PLL. When a first monitored output of the ID circuit appears successively over two horizontal cycles, a burst ID processing for the PLL is actuated. When a second monitored output of the ID circuit follows after the first monitored output, the alternation timing of the reference signal is forcibly shifted by the switch.

Abstract: A multiplier circuit is equipped with first and second differential amplifier circuits and a load circuit. These differential amplifier circuits are comprised of differential pairs of transistors for amplifying a first signal and outputting mutually opposed differential output signals. A switching circuit is comprised of two groups of differential pairs of transistors. In order to increase the dynamic range of the output signals, this switching circuit controls the base voltage of the differential amplifier pair of transistors, which are constructed of the first and second differential amplifier circuits, and alternately operates these first and second differential amplifier circuits. Accordingly, an opposing signal of the output signals of these first and second differential amplifier circuits is supplied to the load circuit.