Coupling circuit between high impedance piezoelectric signal source and utilizing circuit
US4490639A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 6, 1983 |
| Grant date | Dec 25, 1984 |
| Priority date | — |
| Expiry date | Sep 6, 2003 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S310/80
Abstract
The high impedance output of a touch-sensitive piezoelectric sensor is coupled directly to the high impedance input of a CMOS (complementary metal oxide silicon field effect transistor pair). The CMOS is protected on its input side by clamps which restrict the voltage swing applied to the gates to within the range defined by the positive and negative CMOS bias supply (+V.sub.DD and -V.sub.SS). The sensor produces voltages of approximately equal magnitude in response to slow acting temperature changes and quicker acting manual touching. In order to distinguish piezoelectric from pyroelectric signals, the CMOS bias is periodically and briefly shorted, to ensure a brief return-to-zero of the sensor output, thereby effectively suppressing the slow acting pyroelectric signal without interfering with sensing of quick acting piezoelectric signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.