Electricity: power supply or regulation systems – Self-regulating – Using a three or more terminal semiconductive device as the...
Patent
1982-04-21
1984-09-25
Wong, Peter S.
Electricity: power supply or regulation systems
Self-regulating
Using a three or more terminal semiconductive device as the...
307297, 330288, 330300, G05F 320
Patent
active
044737947
ABSTRACT:
An integrated circuit amplifier for a high impedance microphone (100) of the capacitance type is disclosed. The subject amplifier circuit permits the further miniaturization of an electret microphone as it is capable of providing an input impedance simulating a resistor value of hundreds of megohms. The circuit particularly comprises duplicate coupling circuits (101a and 101b), a source of reference direct current voltage (103), and a gain providing circuit (102). The coupling circuits (101a and 101b) comprise a first pair of diodes (Q1 and Q2) symetrically placed about one input terminal (IN1) of the microphone (100). Outputs of the reference voltage source (103) are provided to coupling circuits (101a and 101b) and through the coupling circuits to gain providing circuit 102. Such an arrangement facilitates power supply noise rejection and automatic canceling of direct current voltage drifts. A current repeater circuit (FIG. 8) is employed generally throughout the integrated circuit amplifier for driving various elements. The current repeater comprises at least one unipolar transistor to permit operation at low direct current voltages, while providing an accurately controlled current transfer ratio.
REFERENCES:
patent: 3806742 (1974-04-01), Powell
patent: 3922596 (1975-11-01), Cave et al.
patent: 4008441 (1977-02-01), Schade, Jr.
Early Scott H.
Minear Roger L.
AT&T Bell Laboratories
Newman H. L.
Wong Peter S.
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