CMOS Bridge for capacitive pressure transducers

Details CMOS Bridge for capacitive pressure transducers CMOS Bridge for capacitive pressure transducers

1982-11-10

1984-07-17

Goldberg, Gerald

Measuring and testing

Fluid pressure gauge

Electrical

73708, 73724, 73780, G01L 1904

Patent

active

044598564

ABSTRACT:
A fixed reference capacitance (10) and a variable, pressure sensitive capacitance (12) are defined by a common conductive layer (14), and a common dielectric layer (16). A peripheral conductive layer 20 completes the reference capacitor and a central conductive layer (22) completes the variable capacitor. A peripheral supporting layer or structure (18) prevents the thickness or the dielectric constant of the dielectric layer peripheral portion but not the central portion from varying in response to pressure changes. In this manner, the reference and variable capacitors may be placed closely adjacent without pressure isolating the reference capacitor. An oscillator (30) provides an AC, such as square wave, driving signal to first and second temporary storage capacitors (52, 54). A bridge (70) of CMOS transistors selectively connects the first and second storage capacitors with the reference and variable capacitors. A gating control circuit (90) selectively gates the CMOS transistors of the bridge conductive and nonconductive such that during a positive square wave half cycle, the first storage capacitor is connected with the reference capacitor and the second storage capacitor is connected with the variable capacitor and during a negative half cycle the first storage capacitor is connected with the variable capacitor and the second storage capacitor is connected with the reference capacitor.

REFERENCES:
patent: 3869676 (1975-03-01), Harrison et al.
patent: 4149096 (1979-04-01), Holzner
patent: 4215277 (1980-07-01), Weiner
patent: 4289035 (1981-09-01), Lee
patent: 4387601 (1983-06-01), Azegami
patent: 4422335 (1983-12-01), Ohnesurge

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