Tuning circuit

A tuning ciruit including a plurality of cascade connected tuning amplifier sections having their tuning frequencies shifted by a given frequency, each of said tuning amplifier sections comprising:

• an adding circuit for adding an input signal applied to one end of an input impedance element and a feedback signal applied to one end of a feedback impedance element;
• a pair of phase shifting circuits of opposite phase shift directions to each other and including a series circuit of a first resistor and capacitor or an inductor, and a differential input amplifier;
• and
• a first voltage dividing circuit for dividing an input AC signal by a predetermined dividing ratio;
• wherein said pair of phase shifting circuits and said first voltage dividing circuits are connected in a cascade manner, the added signal from said adding circuit is applied to the first stage circuit of said plurality of cascade connected circuits, an output signal from the final stage ciruit is applied through said voltage dividing circuit to the one end of said feedback impedance element as the feedback signal, and the signal to be applied to said voltage dividing circuit is derived as the output signal and wherein all constituent components are integrally formed on a semiconductor substrate.

A tuning circuit including a plurality of cascade connected tuning amplifier sections each having substantially equal tuning frequency, each of said tuning amplifier sections comprising:

• an adding circuit for adding an input signal applied to one end of an input impedance element and a feedback signal applied to one end of a feedback impedance;
• a pair of phase shifting circuits of mutually opposite phase shift directions including a series circuit of a first resistor and a capacitor or an inductor and a differential input amplifier;
• and
• a first voltage dividing circuit for dividing an input AC signal thereto by a desired dividing ratio;
• wherein said pair of phase shifting circuits and said first voltage dividing circuit are connected in a cascade manner, the added signal from said adding circuit is applied to the input stage of said plurality of cascade connected circuits, the output from the final stage circuit is applied to the one end of said feedback impedance element, and the input to said voltage dividing circuit is derived as the output signal, wherein at least one of said pair of phase shifting circuits includes a second resistor connected to the inverting input terminal of said differential input amplifier through which an AC signal is applied, a second voltage dividing circuit connected to the output terminal of said differential amplifier, a third resistor interposed between the output of said second voltage dividing circuit and the inverting input terminal of said differential input amplifier, and said series circuit, and wherein the junction point of said first resistor and said capacitor or inductor constituting said series circuit is connected to the non-inverting input terminal of said differential input amplifier.

A tuning circuit including a plurality of cascade connected tuning amplifier sections each having substantially equal tuning frequency, each of said tuning amplifier sections comprising:

• an adding circuit for adding an input signal applied to one end of an input impedance element and a feedback signal applied to one end of a feedback impedance;
• a pair of phase shifting circuits of mutually opposite phase shift directions including a series circuit of a first resistor and a capacitor or an inductor and a differential input amplifier;
• and
• a first voltage dividing circuit for dividing an input AC signal thereto by a desired dividing ratio;
• wherein said pair of phase shifting circuits and said first voltage dividing circuit are connected in a cascade manner, the added signal from said adding circuit is applied to the input stage of said plurality of cascade connected circuits, the output from the final stage circuit is applied to the one end of said feedback impedance element, and the input to said voltage dividing circuit is derived as the output signal, wherein at least one of said pair of phase shifting circuits includes a second resistor connected to the inverting input of said differential input amplifier through which an AC signal is applied, a third resistor interposed between the inverting input and output terminals of said differential input amplifier, a fourth resistor connected between the inverting input terminal of said differential input amplifier and ground, and said series circuit, and wherein the junction point of said first resistor and said capacitor or inductor constituting said series circuit is connected to the non-inverting input terminal of said differential input amplifier.

A tuning circuit including a plurality of cascade connected tuning amplifier sections having their tuning frequencies shifted by a given frequency, each of said tuning amplifier sections comprising:

• an adding circuit for adding an input signal applied to one end of an input impedance element and a feedback signal applied to one end of a feedback impedance element;
• a pair of phase shifting circuits of opposite phase shift directions to each other and including a series circuit of a first resistor and a capacitor or an inductor, and a differential input amplifier;
• and
• a first voltage dividing circuit for dividing an input AC signal by a predetermined dividing ratio;
• wherein said pair of phase shifting circuits and said first voltage dividing circuit are connected in a cascade manner, the added signal from said adding circuit is applied to the first stage circuit of said plurality of cascade connected circuits, an output signal from the final stage circuit is applied to the one end of said feedback impedance element as the feedback signal, and the signal to be applied to said voltage dividing circuit is derived as the output signal, wherein at least one of said pair of phase shifting circuits comprises a second resistor connected to the inverting input terminal of said differential input amplifier to receive an AC signal therethrough, a second voltage dividing circuit connected to the output terminal of said differential input amplifier, a third resistor coupled between the output terminal of said second voltage dividing circuit and the inverting input terminal of said differential input amplifier, and said series circuit, and wherein the junction point of said first resistor and said capacitor or said inductor constituting said series circuit is connected to the non-inverting input terminal of said differential input amplifier.