Patent US3629720A successfully refreshed from Google Patents.
US3629720A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digitally controlled variable-gain linear dc amplifier
Assignee: University of Toronto Innovations Foundation
•
Filing: 1970-03-12
•
Granted: 1971-12-21
•
Expires: 1990-03-12
Abstract
Abstract A digitally controlled variable gain linear DC amplifier consisting of a resistance bridge in which the resistance of one arm is determined by ''''n'''' binary weighted resistors connected in parallel and adapted to be switched in or out of the circuit by a n-bit binary control signal has its output connected to the input of an operational amplifier having a feedback resistor of equal value to the resistance of one arm of the bridge. The gain of the amplifier is determined by the resistance value of the ''''n'''' binary weighted resistors in relation to the resistances in the other arms of the bridge and the feedback-resistance of the amplifier.
Inventors
- 👤 Adel S Sedra
- 👤 Kenneth C Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:07
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/001
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
164 words
A digitally controlled variable gain linear DC amplifier comprising: a. an operational amplifier having a feedback resistor, b. a voltage divider network of first and second resistors in series and equal in value, with the midpoint connected to the noninverting input of the amplifier such that one half of any input voltage connected across the resistors in series would be applied to the amplifier, c. a third resistor equal in value to the feedback resistor, d. a series of ''''n'''' binary weighted resistors in series with switching devices connected in parallEl to provide an overall resistance whose value is determined by the condition of the switching devices, said switching devices adapted to be operable by a ''''n''''-bit switching control signal, e. said third resistor and said overall resistance connected in series with the junction point connected to the inverting input of the amplifier and adapted to be connected to an input voltage of equal magnitude of that applied to the first and second resistors.
Claim 2
Dependent Claim
164 words
A digitally controlled variable gain linear DC amplifier comprising: a. an operational amplifier having a feedback resistor, b. a voltage divider network of first and second resistors in series and equal in value, with the midpoint connected to the noninverting input of the amplifier such that one half of any input voltage connected across the resistors in series would be applied to the amplifier, c. a third resistor equal in value to the feedback resistor, d. a series of ''''n'''' binary weighted resistors in series with switching devices connected in parallEl to provide an overall resistance whose value is determined by the condition of the switching devices, said switching devices adapted to be operable by a ''''n''''-bit switching control signal, e. said third resistor and said overall resistance connected in series with the junction point connected to the inverting input of the amplifier and adapted to be connected to an input voltage of equal magnitude of that applied to the first and second resistors.
Claim 3
Dependent Claim
128 words
A digitally controlled variable gain linear DC amplifier comprising: a. a resistance bridge adapted for connection to a supply voltage, with two adjacent arms containing resistors of equal value, a third arm containing a resistor of known value, and a fourth arm having a resistance value determined by ''''n'''' binary weighted resistors connected in parallel and adapted to be switched in or out of the circuit by a n-bit binary control signal such as to alter the resistance value of the fourth arm in relation to the magnitude of the binary control signal, and b. an operational amplifier having a feedback resistor of equal value to the third arm resistor in the bridge and having its inverting and noninverting terminals connected across the output terminals of the bridge.
Claim 4
Dependent Claim
128 words
A digitally controlled variable gain linear DC amplifier comprising: a. a resistance bridge adapted for connection to a supply voltage, with two adjacent arms containing resistors of equal value, a third arm containing a resistor of known value, and a fourth arm having a resistance value determined by ''''n'''' binary weighted resistors connected in parallel and adapted to be switched in or out of the circuit by a n-bit binary control signal such as to alter the resistance value of the fourth arm in relation to the magnitude of the binary control signal, and b. an operational amplifier having a feedback resistor of equal value to the third arm resistor in the bridge and having its inverting and noninverting terminals connected across the output terminals of the bridge.
Claim 5
Dependent Claim
47 words
A digitally controlled variable gain linear DC amplifier as in claim 2 wherein the ''''n'''' binary weighted resistors are each connected to a switching transistor connected in the inverted mode and adapted to be controlled by the appropriate signal bit of the ''''n'''' bit binary control signal.
Claim 6
Dependent Claim
24 words
A circuit as in claim 2 wherein the feedback resistor and the resistors in three arms of the bridge are all equal in value.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-20 | 1975-06-21 | 1975-12-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-20 | 1979-06-21 | 1979-12-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-20 | 1983-06-21 | 1983-12-21 | $7700.00 | Window Closed / Lapsed |