Patent US4609877A successfully refreshed from Google Patents.
US4609877A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Buffer circuit with differential structure for measurement of capacitive charges
Assignee: STMicroelectronics SRL
•
Filing: 1985-11-07
•
Granted: 1986-09-02
•
Expires: 2005-11-07
Abstract
Abstract In a buffer with an operational amplifier having two inputs and two outputs and two feedback capacitances are inserted two other capacitances which in the measurement stage are switched in parallel to the feedback ones with opposite sign in such a manner as to cancel out the effects on the output voltage signal.
Inventors
- 👤 Germano Nicollini
- 👤 Daniel Senderowicz
- 👤 Pierangelo Confalonieri
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 13:03
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/24
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
82 words
Buffer circuit with differential structure for measurement of capacitive charges comprising an operational amplifier with two inputs, two outputs and a pair of feedback capacitances between said outputs and the corresponding inputs characterized in that it comprises another pair of capacitances the same as said feedback capacitances and commutating devices for connecting alternatively each of said other capacitances between a respective output of the amplifier and a polarization potential or between said amplifier output and the input corresponding to the other output.
Claim 2
Dependent Claim
82 words
Buffer circuit with differential structure for measurement of capacitive charges comprising an operational amplifier with two inputs, two outputs and a pair of feedback capacitances between said outputs and the corresponding inputs characterized in that it comprises another pair of capacitances the same as said feedback capacitances and commutating devices for connecting alternatively each of said other capacitances between a respective output of the amplifier and a polarization potential or between said amplifier output and the input corresponding to the other output.
Claim 3
Dependent Claim
51 words
Buffer circuit according to claim 1 characterized in that it comprises other commutating devices synchronized with the abovementioned ones for connection of a capacitance being measured in parallel with said feedback capacitance simultaneously with connection of said other capacitances between said amplifier output and the input corresponding to the other output.
Claim 4
Dependent Claim
20 words
Buffer circuit according to claim 1 characterized in that said polarization potential is equal to the amplifier input polarization potential.
References Cited (Backward Citations)
US4190805A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-09-01 | 1990-03-03 | 1990-09-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-09-01 | 1994-03-03 | 1994-09-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-09-01 | 1998-03-03 | 1998-09-02 | $7700.00 | Window Closed / Lapsed |