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US 9,000,844 B2Granted
Power efficient transconductance amplifier apparatus and systems
AssigneeTexas Instruments Incorporated
InventorCharles Parkhurst
Life of this patent
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Abstract
Embodiments and methods herein operate as two-stage voltage controlled current sources (i.e., dynamic current sources) operating in class AB mode. Phase-delayed current injection circuits are associated with first-stage bias, second-stage bias, or both. The current injection circuits operate to quickly re-charge inter-stage parasitic capacitance associated with the active side of the class AB dynamic current source shortly after that side becomes inactive. Doing so quickly dissipates an otherwise slowly-decaying residual drive signal to prevent the output stage from continuing to conduct after the associated side of the current source becomes inactive. Excessive current consumption and possible destructive operation of the output stage are mitigated as a result.
Claims18
A dynamic current source, comprising:
- positive side and negative side differential input transconductance devices arranged as a long-tailed pair to accept a differential input signal;
- a positive side phase-dependent current source communicatively coupled to an output of the positive side differential input transconductance device to provide current for positive side output signal recovery during a phase period when the differential input signal no longer activates the positive side of the dynamic current source;
- a negative side phase-dependent current source communicatively coupled to an output of the negative side differential input transconductance device to provide current for negative side output signal recovery during a phase period when the differential input signal no longer activates the negative side of the dynamic current source,
- a master current mirror communicatively coupled to the pair of differential input transconductance devices to provide bias current to the pair of differential input transconductance devices;
- and
- a master current source coupled to the master current mirror to provide root current to the master current mirror.
3 more elements
A dynamic current source, comprising:
- a positive side output transconductance device and a negative side output transconductance device, the output transconductance devices arranged as a long-tailed pair to source current in an amount proportional to a differential signal appearing at differential inputs to the dynamic current source;
- a positive side bias circuit coupled to a positive side input node associated with the positive side output transconductance device, the positive side bias circuit configured to phase-delay a positive side drive signal appearing at the positive side input node and to inject a recovery current proportional to the phase-delayed positive side drive signal into the positive side input node in order to force a residual signal held by parasitic capacitance at the positive side input node to a quiescent state when the differential input signal no longer activates a positive side of the dynamic current source;
- and
- a negative side bias circuit coupled to an negative side input node associated with the negative side output transconductance device, the negative side bias circuit configured to phase-delay a negative side drive signal appearing at the negative side input node and to inject a recovery current proportional to the phase-delayed negative side drive signal into the negative side input node in order to force a residual signal held by parasitic capacitance at the negative side input node to a quiescent state when the differential input signal no longer activates a negative side of the dynamic current source,
- at least one of the positive side bias circuit or the negative side bias circuit further comprising:
- a first bias transconductance device channel-coupled between the corresponding input node and a negative feedback resistor to ground, current through the first bias transconductance device and through the feedback resistor to decrease as the corresponding output transconductance device is driven to conduct, resulting in a decreased voltage drop across the feedback resistor;
- a second bias transconductance device channel-coupled in series with the feedback resistor to ground and with current channels associated with third and fourth bias transconductance devices, the second bias transconductance device to increase channel current through the second, third, and fourth bias transconductance devices in response to an increased control bias voltage at the second bias transconductance device resulting from the decreased voltage drop across the feedback resistor;
- and
- a fifth bias transconductance device coupled to the fourth bias transconductance device to form an output side of a signal recovery current mirror and to inject the recovery current into the corresponding input node.
6 more elements
A power control system, comprising:
- positive and negative side differential input transconductance devices associated with a dynamic current source, the differential input transconductance devices arranged as a long-tailed pair to accept a differential input signal;
- a positive side phase-dependent current source communicatively coupled to an output of the positive side differential input transconductance device to provide current for positive side output signal recovery during a phase period when the differential input signal no longer activates the positive side of the dynamic current source;
- a negative side phase-dependent current source communicatively coupled to an output of the negative side differential input transconductance device to provide current for negative side output signal recovery during a phase period when the differential input signal no longer activates the negative side of the dynamic current source;
- a positive side output transconductance device and a negative side output transconductance device, the output transconductance devices arranged as a long-tailed pair to source current from the dynamic current source in an amount proportional to the differential input signal;
- a positive side bias circuit coupled to a positive side input node corresponding to the positive side output transconductance device, the positive side bias circuit configured to phase-delay a positive side drive signal appearing at the positive side input node and to inject a recovery current proportional to the phase-delayed positive side drive signal into the positive side input node in order to force a residual signal held by parasitic capacitance at the positive side input node to a quiescent state when the differential input signal no longer activates a positive side of the dynamic current source;
- and
- a negative side bias circuit coupled to an negative side input node associated with the negative side output transconductance device, the negative side bias circuit configured to phase-delay a negative side drive signal appearing at the negative side input node and to inject a recovery current proportional to the phase-delayed negative side drive signal into the negative side input node in order to force a residual signal held by parasitic capacitance at the negative side input node to a quiescent state when the differential input signal no longer activates a negative side of the dynamic current source.
4 more elements
Dependencies are inferred from the claim text.