Amplifiers – With semiconductor amplifying device – Including signal feedback means
Patent
1997-03-12
1999-03-23
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including signal feedback means
330 98, 330305, 330306, 327553, 327557, H03F 134
Patent
active
058865802
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a tuned amplifier capable of easily implementing in an integrated circuit, more specifically to a tuned amplifier capable of adjusting the tuned frequency and the maximum attenuation to any desired value without interaction.
BACKGROUND OF INVENTION
Various types of amplifiers using active devices and reactance elements have been proposed as tuned amplifiers and are practically used for certain applications.
Disadvantages of such conventional tuned amplifiers include interaction between the tuned frequency and the maximum attenuation, i.e., an adjustment of the tuned frequency accompanies a change in the maximum attenuation and also an adjustment of the maximum attenuation accompanies a change in the tuned frequency.
Additionally, it is difficult to implement in an integrated circuit the tuned amplifier free from such interaction between the tuned frequency and the maximum attenuation.
It is, therefore, an object of the present invention to overcome the above-mentioned disadvantages of the conventional tuned amplifiers.
DISCLOSURE OF INVENTION
The tuned amplifier according to the present invention comprises an input impedance element to receive an input signal at one end, a feedback impedance element to receive a feedback signal at one end, a summing circuit to add the input signal and the feedback signal, a pair of phase shift circuits connected in a cascade manner each comprising a first series circuit of first and second resistors of substantially equal resistance to receive an input AC signal across both ends thereof, a second series circuit of a third resistor and a capacitor to receive the input AC signal across both ends thereof, and a differential amplifier to amplify by a predetermined amplification factor the difference in potential between the junction of the first and second resistors in the first series circuit and the junction of the third resistor and the capacitor in the second series circuit. The phase shift circuits are connected in a cascade manner. A front stage of the pair of phase shift circuits is configured to receive the output from the summing circuit and to receive the feedback signal from the subsequent stage of the phase shift circuits through the feedback impedance. A tuned signal is derived from the output of either one of the phase shift circuits.
Also, the tuned amplifier according to the present invention comprises an input impedance element to apply an input signal to an input end, a feedback impedance element to apply a feedback signal to the input end, a summing circuit to add the input signal and feedback signal, a pair of phase shift circuits each comprising a first series circuit of first and second resistors of substantially equal resistance to receive an input AC signal across both ends thereof, a second series circuit of a third resistor and a capacitor to receive the input AC signal across both ends thereof, a differential amplifier for amplifying by a predetermined amplification factor the difference in potential at the junction of the first and second resistors in the first series circuit and the junction of the third resistor and the capacitor in the second series circuit, and a non-inverting circuit to output the input AC signal without altering the phase. The pair of phase shift circuits and the non-inverting circuit are connected in a cascade manner. The added signal from the summing circuit is applied as an input to a first stage of the cascade connected circuits. The output from a final stage is applied to the input end as the feedback signal by way of the feedback impedance element. A tuned signal is derived as an output from either one of the cascade connected circuits.
The tuned amplifier according to the present invention comprises a summing amplifier to add an input signal applied thereto by way of an input impedance element and a feedback signal applied thereto by way of a feedback impedance, and a pair of phase shift circuits, each comprising a first series circuit having first and second re
REFERENCES:
patent: 3707685 (1972-12-01), Geffe
Ikeda Takeshi
Ohe Tadataka
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