US4720686A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for converting a fully differential amplifier to a single-ended output amplifier
Assignee: Motorola Solutions Inc
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Filing: 1987-01-14
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Granted: 1988-01-19
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Expires: 2007-01-14
Abstract
Abstract A circuit which converts differential outputs of a fully differential amplifier to a single output using a buffer amplifier is provided. The fully differential amplifier has common-mode feedback provided by a differential feedback stage. An input of the common-mode differential feedback stage is connected to a predetermined one of the differential outputs to maintain the predetermined output at a reference voltage potential. The buffer amplifier uses diffused or well resistors and a single-ended differential amplifier. The buffer amplifier has a balanced structure which minimizes noise and resistor nonlinearity output errors. The circuit also maintains excellent power supply rejection.
Inventors
- 👤 Alan L. Westwick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 03:50
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/45; H03F3/45071; H03F3/45479
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
116 words
A circuit for converting first and second outputs of a fully differential amplifier to a single output, comprising: common-mode output voltage control means coupled to the fully differential amplifier for maintaining a predetermined output common-mode voltage of the two outputs of the fully differential amplifier, said control means having a first input connected directly to a predetermined one of the first or second outputs of the fully differential amplifier and having a second input coupled to a reference voltage terminal, and an output for controlling the first and second outputs of the fully differential amplifier; and output buffer means coupled to the first and second outputs of the fully differential amplifier for providing the single output.
Claim 2
Dependent Claim
116 words
A circuit for converting first and second outputs of a fully differential amplifier to a single output, comprising: common-mode output voltage control means coupled to the fully differential amplifier for maintaining a predetermined output common-mode voltage of the two outputs of the fully differential amplifier, said control means having a first input connected directly to a predetermined one of the first or second outputs of the fully differential amplifier and having a second input coupled to a reference voltage terminal, and an output for controlling the first and second outputs of the fully differential amplifier; and output buffer means coupled to the first and second outputs of the fully differential amplifier for providing the single output.
Claim 3
Dependent Claim
201 words
A circuit for converting first and second outputs of a fully differential amplifier to a single output, comprising: common-mode output voltage control means coupled to the fully differential amplifier for maintaining a predetermined output common-mode voltage, said control means having a first input connected directly to a predetermined one of the first or second outputs of the fully differential amplifier and having a second input coupled to a reference voltage terminal; a single-ended differential amplifier having first and second inputs and an output; a first resistor having a first terminal coupled to the first output of the fully differential amplifier and a second terminal coupled to the first input of the single-ended differential amplifier; a second resistor having a first terminal coupled to the second terminal of the first resistor, and a second terminal coupled to the output of the single-ended differential amplifier; a third resistor having a first terminal coupled to the second output of the fully differential amplifier and a second terminal coupled to the second input of the single-ended differential amplifier; and a fourth resistor having a first terminal coupled to the second terminal of the third resistor, and a second terminal coupled to the reference voltage terminal.
Claim 4
Dependent Claim
201 words
A circuit for converting first and second outputs of a fully differential amplifier to a single output, comprising: common-mode output voltage control means coupled to the fully differential amplifier for maintaining a predetermined output common-mode voltage, said control means having a first input connected directly to a predetermined one of the first or second outputs of the fully differential amplifier and having a second input coupled to a reference voltage terminal; a single-ended differential amplifier having first and second inputs and an output; a first resistor having a first terminal coupled to the first output of the fully differential amplifier and a second terminal coupled to the first input of the single-ended differential amplifier; a second resistor having a first terminal coupled to the second terminal of the first resistor, and a second terminal coupled to the output of the single-ended differential amplifier; a third resistor having a first terminal coupled to the second output of the fully differential amplifier and a second terminal coupled to the second input of the single-ended differential amplifier; and a fourth resistor having a first terminal coupled to the second terminal of the third resistor, and a second terminal coupled to the reference voltage terminal.
Claim 5
Dependent Claim
31 words
The circuit of claim 2 wherein the first input of the single-ended differential amplifier is an inverting input and the second input of the single-ended differential amplifier is a noninverting input.
Claim 6
Dependent Claim
35 words
The circuit of claim 2 wherein the first, second, third and fourth resistors are each fabricated in integrated circuit form by diffusing a P conductivity type semiconductor material in an N conductivity type semiconductor material.
Claim 7
Dependent Claim
21 words
The circuit of claim 2 wherein the first, second, third and fourth resistors each have a substantially equal value of resistance.
Claim 8
Dependent Claim
35 words
The circuit of claim 2 wherein the first, second, third and fourth resistors are each fabricated in integrated circuit form by diffusing an N conductivity type semiconductor material in a P conductivity type semiconductor material.
Claim 9
Dependent Claim
247 words
A circuit which provides first and second outputs in response to receiving first and second input voltages and converts the first and second outputs to a single output, comprising: a fully differential amplifier having a first input for receiving the first input voltage, a second input for receiving the second input voltage, and which provides the first and second outputs; common-mode feedback means having a first input connected directly to the first output of the fully differential amplifier, a second input coupled to a reference voltage terminal, and an output for controlling both the first and second outputs of the fully differential amplifier for maintaining a predetermined common-mode output voltage; a first resistor having a first terminal coupled to the first output of the fully differential amplifier, and a second terminal; a second resistor having a first terminal coupled to the second output of the fully differential amplifier, and a second terminal; a single-ended differential amplifier having a first input coupled to the second terminal of the first resistor, a second input coupled to the second terminal of the second resistor, and an output for providing the single output; a third resistor having a first terminal coupled to the first input of the single-ended differential amplifier and a second terminal coupled to the output of the single-ended differential amplifier; and a fourth resistor having a first terminal coupled to the second input of the single-ended differential amplifier and a second terminal coupled to a reference voltage terminal.
Claim 10
Dependent Claim
247 words
A circuit which provides first and second outputs in response to receiving first and second input voltages and converts the first and second outputs to a single output, comprising: a fully differential amplifier having a first input for receiving the first input voltage, a second input for receiving the second input voltage, and which provides the first and second outputs; common-mode feedback means having a first input connected directly to the first output of the fully differential amplifier, a second input coupled to a reference voltage terminal, and an output for controlling both the first and second outputs of the fully differential amplifier for maintaining a predetermined common-mode output voltage; a first resistor having a first terminal coupled to the first output of the fully differential amplifier, and a second terminal; a second resistor having a first terminal coupled to the second output of the fully differential amplifier, and a second terminal; a single-ended differential amplifier having a first input coupled to the second terminal of the first resistor, a second input coupled to the second terminal of the second resistor, and an output for providing the single output; a third resistor having a first terminal coupled to the first input of the single-ended differential amplifier and a second terminal coupled to the output of the single-ended differential amplifier; and a fourth resistor having a first terminal coupled to the second input of the single-ended differential amplifier and a second terminal coupled to a reference voltage terminal.
Claim 11
Dependent Claim
19 words
The circuit of claim 7 wherein the first, second, third and fourth resistors have substantially equal values of resistance.
Claim 12
Independent Claim
115 words
A method of converting first and second outputs of a fully differential amplifier to a single output, comprising the steps of: coupling first and second input voltages to the fully differential amplifier; controlling the common-mode output voltage of the two outputs of the fully differential amplifier with a common-mode feedback amplifier having a first input connected directly to the first output of the fully differential amplifier, a second input coupled to a reference voltage terminal, and an output for controlling the first and second outputs of the fully differential amplifier; and connecting unity gain buffer means directly to both the first and second outputs of the fully differential amplifier means for providing the single output.
Claim 13
Independent Claim
115 words
A method of converting first and second outputs of a fully differential amplifier to a single output, comprising the steps of: coupling first and second input voltages to the fully differential amplifier; controlling the common-mode output voltage of the two outputs of the fully differential amplifier with a common-mode feedback amplifier having a first input connected directly to the first output of the fully differential amplifier, a second input coupled to a reference voltage terminal, and an output for controlling the first and second outputs of the fully differential amplifier; and connecting unity gain buffer means directly to both the first and second outputs of the fully differential amplifier means for providing the single output.
References Cited (Backward Citations)
DE2853829A1
Cited
US4634996A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-01-18 | 1991-07-20 | 1992-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-18 | 1995-07-20 | 1996-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-18 | 1999-07-20 | 2000-01-19 | $7700.00 | Window Closed / Lapsed |