Abstract A reference voltage is applied to the noninverting input of a differential amplifier. The output of the amplifier is connected through a feedback resistor to the inverting input so that the output voltage increases as required to maintain the inverting input at the same potential as the reference voltage. A plurality of resistance branches connect the inverting input to ground. Current through the feedback resistor can be increased incrementally by switching selected resistance branches conductive, thus requiring an increased output voltage in order to maintain the inverting input at the reference voltage. Current through each resistance branch is controlled by a transistor operated in the inverted mode so that the IR drop through the transistor tends to cancel the offset voltage of the transistor. When operated as a digital-to-analog converter, the digital input is used to control the resistance branches and the output of the amplifier produces the analog signal. A step approximation analog-to-digital converter is also described in which the output of the differential amplifier is applied to one input of a comparator and an analog signal applied to one input of a comparator and an analog signal applied to the other input. The resistor branch network is operated by a step approximation logic circuit in a manner to maintain the system balanced. The state of the resistor branch network is representative of the digital output. The reference voltage and analog input voltage may also be reversed.
Inventors
👤 Robert E Young
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-02 15:50
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/002
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
183 words
In a signal converter, the combination of: a differential amplifier having a noninverting input, an inverting input, and an output, feedback resistance means connecting the output to the inverting input, means including a plurality of individually controllable branches each comprised of a precision resistor in series with a transistor operated in the inverted mode with the collector grounded for controlling the current through the feedback resistance means in response to a digital value whereby the output of the amplifier will produce an analog value corresponding to the digital value, the noninverting input being connected to a source of reference potential regulated by a zener diode, and further characterized by a comparator amplifier having a pair of inputs and an output, one of the inputs being connected to the output of the differential amplifier and the other being connected to receive the analog input signal, and logic means responsive to the comparator means for switching the means for controlling the current through the feedback resistance to maintain the output of the differential amplifier in a predetermined relationship with respect to the analog input signal.
Claim 2
Dependent Claim
183 words
In a signal converter, the combination of: a differential amplifier having a noninverting input, an inverting input, and an output, feedback resistance means connecting the output to the inverting input, means including a plurality of individually controllable branches each comprised of a precision resistor in series with a transistor operated in the inverted mode with the collector grounded for controlling the current through the feedback resistance means in response to a digital value whereby the output of the amplifier will produce an analog value corresponding to the digital value, the noninverting input being connected to a source of reference potential regulated by a zener diode, and further characterized by a comparator amplifier having a pair of inputs and an output, one of the inputs being connected to the output of the differential amplifier and the other being connected to receive the analog input signal, and logic means responsive to the comparator means for switching the means for controlling the current through the feedback resistance to maintain the output of the differential amplifier in a predetermined relationship with respect to the analog input signal.