Amplifiers – Sum and difference amplifiers
Patent
1998-06-15
2000-03-07
Pascal, Robert
Amplifiers
Sum and difference amplifiers
330305, H03F 345
Patent
active
060345667
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a tuning amplifier easy to be integrated, particularly to a tuning amplifier which can make an optional adjustment of tuning frequency and a maximum attenuation without interference to each other.
BACKGROUND OF ART
Various kinds of the tuning amplifiers using active elements and reactance elements have been conventionally proposed and put to practical use.
For example, the tuning amplifier of the prior art utilizing LC resonance is characterized in that when the tuning frequency is adjusted, Q and a gain depending on a LC circuit are varied, and when the maximum attenuation is adjusted, the tuning frequency is varied, and when the maximum attenuation is adjusted, the gain in the tuning frequency is varied. Consequently, in the tuning amplifier of the prior art, it was extremely difficult to adjust the tuning frequency, the gain in the tuning frequency and the maximum attenuation of C1, C2 without interference to each other. Also, it was difficult to form the tuning amplifier capable of adjusting the tuning frequency and the maximum attenuation by an integrated circuit.
DISCLOSURE OF THE INVENTION
It is the object of the present invention to solve the above problems and to provide a tuning amplifier enable to adjust the tuning frequency, the gain of the tuning frequency, the maximum attenuation without interference therebetween, particularly enable to suppress the amplitude fluctuation in case of the tuning frequency is varied.
The tuning amplifier according to the present invention comprises two phase shifting circuits of a full band pass type including a differential amplifier wherein an output is returned to the input side, a voltage dividing circuit interposed into one part of the feedback loop formed by connecting in cascade each of said two phase shifting circuits. The added signal from said adding circuit is applied to the front stage phase shifting circuit of said two phase shifting circuits connected in cascade, the output signal from the subsequent stage phase shifting circuit is applied to said adding circuit as said feedback signal. An AC signal input to said voltage dividing circuit is output as said tuned signal.
The tuning amplifier according to the present invention comprises 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, two phase shifting circuits including a differential amplifier wherein one end of a first resistor is connected to the inverting input terminal and an AC signal is applied by way of said first resistor, a first voltage dividing circuit connected to the output terminal of said differential amplifier, a second resistor interposed between the output terminal of said first voltage dividing circuit and the inverting input terminal of said differential amplifier, and a series circuit constituted by a reactance element using a capacitor or an inductor and a third resistor and connected to the other end of said first resistor. The junction point of said third resistor and said reactance element is connected to the non-inverting input terminal of said differential amplifier.
Each of said two phase shifting circuits are connected in cascade. The added signal from said adding circuit is applied to the front stage phase shifting circuit of said two phase shifting circuits connected in cascade and the output signal from the subsequent stage phase shifting circuit is applied to one end of said feedback impedance element. The output of either one of the two phase shifting circuits is output as the tuned signal.
The tuning amplifier according to the present invention comprises 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, two phase shifting circuits including a differential amplifier wherein one end of a first resistor is connected to the inverting input terminal and an AC signal is applied by wa
REFERENCES:
patent: 3434070 (1969-03-01), Bartnik et al.
patent: 3972006 (1976-07-01), Ruegg
patent: 4023113 (1977-05-01), Mathias
patent: 5886580 (1999-03-01), Ikeda et al.
Choe Henry
Pascal Robert
Takeshi Ikeda
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