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US 5,202,655 AGranted
Microwave active filter circuit using pseudo gyrator
AssigneeSharp Kabushiki Kaisha
InventorShinji Hara
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Abstract
A low pass filter using two pseudo gyrators 10 and 20 is disclosed. The gate-source capacitances of field effect transistors forming the pseudo gyrator circuit can be considered to be included in capacitors for forming the low pass filter. Therefore, an ideal admittance matrix for a gyrator is obtained. Increase in integration density of the low pass filter can be achieved since the low pass filter is formed by a simplified pseudo gyrator circuit.
Claims7
An active filter circuit comprising:
- cascaded first and second pseudo gyrator means,
- first capacitor means connected between an input node of said first pseudo gyrator means and a predetermined reference potential,
- a second capacitor means connected between a common connection node of an output node of said first pseudo gyrator means and an input node of said second pseudo gyrator means and the reference potential, and
- third capacitor means connected between an output node of the second pseudo gyrator means and the reference potential,
- wherein each of said first and second pseudo gyrator means comprises
- first inverting amplifier means including a first field effect transistor,
- second inverting amplifier means coupled to the output of said first inverting amplifier means, and including a second field effect transistor,
- said first field effect transistor having a gate electrode coupled to the input node of a corresponding pseudo gyrator means, and a source electrode connected to reference potential,
- said second field effect transistor having a gate electrode coupled to a drain electrode of said first field effect transistor, a source electrode connected to the reference potential, and a drain electrode coupled to an output node of said corresponding pseudo gyrator means,
- negative feedback means for feeding back negatively the voltage of the output node of said corresponding pseudo gyrator means to the input node.
7 more elements
An active filter circuit comprising:
- cascaded first and second pseudo gyrator means,
- first capacitor means connected between an input node of said first pseudo gyrator means and a predetermined reference potential,
- second capacitor means connected between a common connection node of an output node of said first pseudo gyrator means and an input node of said second pseudo gyrator means and the reference potential, and
- third capacitor means connected between an output node of said second pseudo gyrator means and the reference potential,
- wherein each of said first and second pseudo gyrator means comprises
- cascaded first and second inverting amplifier means, each having an input impedance,
- negative feedback means for applying negative feedback to said cascaded first and second inverting amplifier means, and
- resistor means coupled between a common connection node of said first and second inverting amplifier means and the reference potential,
- wherein the resistance of said resistor means is small enough to be substantially negligible in comparison with the input impedance of said first and second inverting amplifier means.
6 more elements
Dependencies are inferred from the claim text.