Amplifiers – With semiconductor amplifying device – Including signal feedback means
Patent
1985-12-19
1987-03-31
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including signal feedback means
330286, 330297, H03F 114
Patent
active
046546030
ABSTRACT:
A low input-capacitance amplifier is disclosed for utilization in driving a guard shield of a high impedance signal. The high impedance signal is applied to a central conductor and to the input of a first unity gain amplifier. The output of that unity gain amplifier is applied to a second unity gain amplifier which is utilized to provide the guard signal to the shield conductor and also to provide electrical power to the first unity gain amplifier. A preferred embodiment of the present invention is utilized in conjunction with a highly sensitive capacitance proximity sensor which has a sense electrode remotely located from the associated electronic circuitry. By utilizing the output of the second unity gain amplifier as the power source for the first amplifier the input, the output and all electrical power receiving nodes are maintained at substantially identical electrical potentials thereby nullifying the loading effect of any parasitic capacitances at the input of the first amplifier circuitry.
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patent: 3253225 (1966-05-01), Dalton et al.
patent: 3995175 (1976-11-01), Hoyt et al.
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1984 D.A.T.A. Book, vol. 29, Book 2, Mar. 1984, pp. 24, 145.
Krakauer, "Electrometer Triode Follower", The Review of Scientific Instruments, vol. 24, No. 7, Jul. 1953, pp. 496-500.
Thomas, "Microelectrode Amplifier with Improved Method of Input-Capacitance Neutralization", Medical and Biological Engineering & Computing, vol. 15, No. 4, Jul. 1977, pp. 450-454.
Thomas, "Input Capacitance Feedback Improves Neutralization", Electronics, Jan. 20, 1977, pp. 112, 113.
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