Merged differential amplifier and current source
AssigneeNorth American Philips Corporation, Signetics Division
InventorsWilliam D. Mack, Daniel J. Linebarger
Life of this patent
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Abstract
The tail current of a differential transistor pair (12 and 14) is controlled by a feed-back means (40) that couples the pair's tail node (16) to the control input of each transistor for controlling a biasing current through each transistor. The control input of each transistor further receives an input signal in addition to an output signal of the feed-back means. As a result, the circuit has a stable and accurate tail current, and in addition is suitable for a low-voltage supply or for high-current operation.
Claims13
An electronic circuit comprising:
- first and second signal input nodes for receiving first and second input signals;
- first and second active devices each having (i) a main current path and (ii) a device input coupled to a respective one of the signal input nodes for control of the main current path;
- a current source coupled to the main current paths via a tail node for biasing the active devices;
- and
- feed-back means that provides a common-mode coupling from the tail node to each device input for controlling a bias current through each main current path in response to a control signal, different from the first and second input signals, applied to the feed-back means, wherein the feed-back means includes:
- a differential amplifier with a first input for receiving the control signal, a second input coupled to the tail node, and an output, and
- a resistive coupling between the amplifier's output and each device input.
An electronic circuit comprising:
- first and second signal input nodes for receiving first and second input signals;
- first and second active devices each having (i) a main current path and (ii) a device input coupled to a respective one of the signal input nodes for control of the main current path;
- a current source coupled to the main current paths via a tail node for biasing the active devices;
- and
- feed-back means that provides a common-mode coupling from the tail node to each device input for controlling a bias current through each main current path in response to a control signal, different from the first and second input signals, applied to the feed-back means, wherein the feed-back means includes:
- a differential amplifier with a first input for receiving the control signal, a second input coupled to the tail node, and an output for providing an amplifier output signal, and
- first and second signal pre-amplifiers respectively responsive to the first and second input signals and responsive to amplifier output signal for controlling the first and second active devices.
Dependencies are inferred from the claim text.