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US 4,365,209 AGranted
Impedance transducer
AssigneeRicoh Company, Ltd.
InventorSatoshi Yamauchi
Life of this patent
Estimating the term…
Abstract
An impedance transducer is shown wherein two active elements of the same characteristics are formed on one thermally conductive base, one of these active elements is connected in a negative feedback circuit of a negative feedback amplifier, and the internal impedance of the other of these active elements is proportional to the input of the negative feedback amplifier.
Claims11
A variable impedance circuit, comprising:
- first and second transistors mounted on a common thermally conductive substrate so that said transistors remain at substantially the same temperature, each transistor having two main electrodes and a control electrode means, said transistors exhibiting essentially the same electrical characteristics at said electrodes;
- a negative feedback amplifier having an input terminal and connected in circuit with said first transistor to vary the impedance between the main electrode means of said first transistor in a predetermined manner in accordance with an impedance control signal applied to said input terminal;
- a memory circuit coupled to said input terminal of said negative feedback amplifier for setting said impedance control signal at a desired value;
- and
- means for maintaining essentially the same electrical condition at each of said control electrode means, so that the impedance presented between the main electrodes of the second transistor is essentially equal to the impedance between the main electrodes of said first transistor.
2 more elements
An impedance transducer comprising a first group of two field-effect transistors which are formed on one thermally conductive base plate and whose gates are connected to each other;
- a second group of field-effect transistors which are formed on a thermally conductive base plate and whose polarity is opposite that of the first group and which are similarly connected;
- two operational amplifiers whose outputs are respectively input to the gates of said field-effect transistors;
- and a memory circuit comprising an integrator which comprises a capacitor and a high input impedance operational amplifier and whose output is input to each of said operational amplifiers;
- wherein each of said transistor groups is used for providing a negative feedback amplification for the corresponding one of said two operational amplifiers;
- means for causing a constant current to flow through the output circuit of one of the transistors of each group for negative feedback amplification, so that an impedance proportional to the potential of the input from said integrator to each of said two operational amplifiers is presented as the internal impedance of the other transistor of each group.
2 more elements
Dependencies are inferred from the claim text.