US4274056A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Charge amplifier with minimum offset voltage
Assignee: Honeywell International Inc
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Filing: 1978-11-08
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Granted: 1981-06-16
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Expires: 1998-11-08
Abstract
Abstract A charge amplifier having minimum offset voltage such as for use in processing a signal from a capacitive transducer. The amplifier is arranged to minimize the offset voltage and drift. The amplifier is arranged to be reset to zero upon application of supply voltage thereto, and the resetting circuit is arranged to reset the amplifier automatically during an adjustable interval after application of the supply voltage. The charge amplifier is further compensated for temperature variation and is arranged at minimum offset voltage notwithstanding strong background noise.The amplifier is arranged to have a drift of no more than a fraction of a millivolt per second. The amplifier circuit includes an improved switching arrangement and may utilize a second amplifier circuit for effecting temperature compensation.
Inventors
- 👤 Henry J. Lukes
- 👤 Walter Kamphorst
- 👤 Romeal F. Asmar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:13
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/45; H03F3/45071; H03F3/45076; H03F3/45475; G; G01; G01R; G01R17/00; G01R19/00; G01R19/0023; H03F3/70; H03F2203/00; H03F2203/45; H03F2203/45212
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
128 words
In a charge amplifier circuit including a charge amplifier, a transducer connected to a source of reference voltage, and a feedback capacitor connected between an inverting input terminal and output terminal of the amplifier, the improvement comprising: double-throw break-before-make switch means alternatively (a) connected across said capacitor shorting the capacitor and concurrently disconnecting said transducer from said inverting input terminal, and (b) connecting said transducer to said inverting input terminal and concurrently discontinuing shorting of the capacitor; and resetting circuit means for selectively operating said switch means to first disconnect the switch means from across the capacitor and subsequently effect connection of the transducer to the inverting input terminal whereby said capacitor is charge-free at the time the switch means connects the transducer to said inverting input terminal.
Claim 2
Dependent Claim
128 words
In a charge amplifier circuit including a charge amplifier, a transducer connected to a source of reference voltage, and a feedback capacitor connected between an inverting input terminal and output terminal of the amplifier, the improvement comprising: double-throw break-before-make switch means alternatively (a) connected across said capacitor shorting the capacitor and concurrently disconnecting said transducer from said inverting input terminal, and (b) connecting said transducer to said inverting input terminal and concurrently discontinuing shorting of the capacitor; and resetting circuit means for selectively operating said switch means to first disconnect the switch means from across the capacitor and subsequently effect connection of the transducer to the inverting input terminal whereby said capacitor is charge-free at the time the switch means connects the transducer to said inverting input terminal.
Claim 3
Dependent Claim
17 words
The charge amplifier circuit of claim 1 wherein said resetting circuit means comprises time delayed gating means.
Claim 4
Dependent Claim
34 words
The charge amplifier circuit of claim 1 wherein said switch means comprises contact means of an electromechanical relay including moving contact means and said resetting circuit effects selective movement of said moving contact means.
Claim 5
Dependent Claim
148 words
In charge amplifier circuit including a charge amplifier, a transducer connected to a source of reference voltage, and a feedback capacitor connected between an inverting input terminal and output terminal of the amplifier, the improvement comprising: a double-throw, break-before-make switch alternatively (a) normally connected across said capacitor shorting the capacitor and concurrently disconnecting said transducer from said inverting input terminal, and (b) connecting said transducer to said inverting input terminal and concurrently discontinuing shorting of the capacitor; resetting circuit means for selectively operating said switch to first disconnect the switch from across the capacitor and subsequently effect connection of the transducer to the inverting input terminal whereby said capacitor is charge-free at the time the switch connects the transducer to said inverting input terminal; and compensating means for reducing offset voltage at the output of the amplifier resulting from imperfect balance of the amplifier components and thermal variations.
Claim 6
Dependent Claim
148 words
In charge amplifier circuit including a charge amplifier, a transducer connected to a source of reference voltage, and a feedback capacitor connected between an inverting input terminal and output terminal of the amplifier, the improvement comprising: a double-throw, break-before-make switch alternatively (a) normally connected across said capacitor shorting the capacitor and concurrently disconnecting said transducer from said inverting input terminal, and (b) connecting said transducer to said inverting input terminal and concurrently discontinuing shorting of the capacitor; resetting circuit means for selectively operating said switch to first disconnect the switch from across the capacitor and subsequently effect connection of the transducer to the inverting input terminal whereby said capacitor is charge-free at the time the switch connects the transducer to said inverting input terminal; and compensating means for reducing offset voltage at the output of the amplifier resulting from imperfect balance of the amplifier components and thermal variations.
Claim 7
Dependent Claim
78 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the offset voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens.
Claim 8
Dependent Claim
86 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said break-before-make switch is switched to connect said transducer to said inverting input terminal.
Claim 9
Dependent Claim
89 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply a portion of the voltage at said output terminal through an RC integrating network and a divider network coupled to the auxiliary amplifier to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens.
Claim 10
Dependent Claim
134 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply a portion of the voltage at said output terminal through an RC integrating network and a divider network coupled to the auxiliary amplifier to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens, said integrator circuit is arranged such that the voltage integrated during the resetting interval is a preselected multiple of that required to effect a desired reduction of the offset voltage and said divider network is arranged to divide the integrated voltage inversely to said multiple.
Claim 11
Dependent Claim
93 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens, said break-before-make switch and said auxiliary switch being portions of a double pole double-throw electromechanical relay.
Claim 12
Dependent Claim
133 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens, and a resistor connecting the inverting input terminal of the auxiliary amplifier to a DC potential source, said RC integrating network including a resistor coupling said normally closed switch to said inverting input terminal of the auxiliary amplifier, and an integrating capacitor connected between said inverting input terminal and the output terminal of the auxiliary amplifier.
Claim 13
Dependent Claim
152 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval during which said normally closed switch opens, and a resistor connecting the inverting input terminal of the auxiliary amplifier to a DC potential source, said RC integrating network including a resistor coupling said normally closed switch to said inverting input terminal of the auxiliary amplifier, and an integrating capacitor connected between said inverting input terminal and the output terminal of the auxiliary amplifier, said integrating capacitor having a capacity at least several orders of magnitude greater than that of said feedback capacitor.
Claim 14
Dependent Claim
152 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply at least a portion of the voltage at said output terminal to said noninverting terminal of the charge amplifier effectively only during the resetting interval during which said normally closed switch opens, and a resistor connecting the inverting input terminal of the auxiliary amplifier to a DC potential source, said RC integrating network including a resistor coupling said normally closed switch to said inverting input terminal of the auxiliary amplifier, and an integrating capacitor connected between said inverting input terminal and the output terminal of the auxiliary amplifier, said integrating capacitor having a capacity at least several orders of magnitude greater than that of said feedback capacitor.
Claim 15
Dependent Claim
142 words
The charge amplifier circuit of claim 4 wherein said compensating means comprises an integrator circuit including an auxiliary amplifier coupled to the noninverting input terminal of said charge amplifier and to the output terminal thereof through a second, normally closed switch to integrate and apply a portion of the voltage at said output terminal through an RC integrating network and a divider network coupled to the auxiliary amplifier to said noninverting terminal of the charge amplifier effectively only during the resetting interval after which said normally closed switch opens, said integrator circuit being arranged such that the voltage integrated during the resetting interval is approximately five times that required to effect a desired reduction of the offset voltage and said divider network is arranged to provide to the charge amplifier noninverting input terminal a voltage approximately one-fifth that of the integrated voltage.
Claim 16
Dependent Claim
62 words
In a charge amplifier circuit including a charge amplifier having an output, and an inverting input, and a feedback capacitor connected between the output and the inverting input, resetting means comprising a double throw break-before-make switch having normally closed contacts connected across said feedback capacitor, and normally open contacts connected between a signal source and said inverting input of the charge amplifier.
Claim 17
Dependent Claim
62 words
In a charge amplifier circuit including a charge amplifier having an output, and an inverting input, and a feedback capacitor connected between the output and the inverting input, resetting means comprising a double throw break-before-make switch having normally closed contacts connected across said feedback capacitor, and normally open contacts connected between a signal source and said inverting input of the charge amplifier.
Claim 18
Dependent Claim
33 words
The charge amplifier circuit of claim 14 including an auxiliary circuit which includes means for providing a predetermined time delay which is initiated by energization thereof and which upon termination energizes said switch.
Claim 19
Dependent Claim
49 words
The charge amplifier circuit of claims 14 or 15 having an output connected through normally closed contacts of a second switch to the input of an auxiliary integrating amplifier, at least a portion of the output voltage of which is fed to said noninverting input of the charge amplifier.
Claim 20
Dependent Claim
28 words
The charge amplifier circuit of claim 16 in which each switch comprises a double pole switch controlled by the same control circuit portion including said time delay means.
Claim 21
Dependent Claim
31 words
The charge amplifier circuit of claim 14 in which an additional resistor is connected from said inverting input of the integrating amplifier to a DC voltage source to compensate for drift.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-06-15 | 1984-12-15 | 1985-06-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-06-15 | 1988-12-15 | 1989-06-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-06-15 | 1992-12-15 | 1993-06-16 | $7700.00 | Window Closed / Lapsed |