Displacement converting circuit arrangement
First Claim
1. A displacement converting circuit arrangement comprising:
- first and second impedance elements, the impedance of at least one of said elements being variable in response to a mechanical displacement thereof;
means for deriving first and second DC currents, said first and second DC currents being proportional to the impedances of said first and second impedance elements, respectively;
means for deriving a current corresponding to the sum of said first and second DC currents;
a field effect transistor having said current corresponding to the sum of said first and second DC currents flowing between its source and drain electrodes, said field effect transistor maintaining said sum current at a constant value;
means for maintaining at least one of said first and second DC currents at a fixed amount;
a differential amplifier having first and second input terminals and an output terminal, said first and second DC currents being supplied to the first and second input terminals respectively of said differential amplifier; and
an output transistor coupled to the output terminal of said differential amplifier, the current at the output of said output transistor corresponding to the difference between said first and second DC currents, said output current indicating the magnitude of said mechanical displacement.
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Accused Products
Abstract
A displacement converting circuit arrangement comprising first and second capacitors in the form of a paired structure, at least one of the capacitors having a capacitance which is varied in response to a mechanical displacement. Means are provided for deriving first and second currents respectively proportional to the capacitances of the first and second capacitors, means for maintaining at least one of the DC currents corresponding to at least one capacitor having a variable capacitance at a fixed amount, and means for producing an output current corresponding to the difference between the DC currents, so that the output current indicates the amount of the mechanical displacement. Operation stability is improved by the simplified circuit arrangement, with consequent reduction in error and circuit failure. The movable electrode for varying the capacitance can withstand a heavy load.
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Citations
14 Claims
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1. A displacement converting circuit arrangement comprising:
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first and second impedance elements, the impedance of at least one of said elements being variable in response to a mechanical displacement thereof; means for deriving first and second DC currents, said first and second DC currents being proportional to the impedances of said first and second impedance elements, respectively; means for deriving a current corresponding to the sum of said first and second DC currents; a field effect transistor having said current corresponding to the sum of said first and second DC currents flowing between its source and drain electrodes, said field effect transistor maintaining said sum current at a constant value; means for maintaining at least one of said first and second DC currents at a fixed amount; a differential amplifier having first and second input terminals and an output terminal, said first and second DC currents being supplied to the first and second input terminals respectively of said differential amplifier; and an output transistor coupled to the output terminal of said differential amplifier, the current at the output of said output transistor corresponding to the difference between said first and second DC currents, said output current indicating the magnitude of said mechanical displacement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification