Supply-noise-rejecting current source
AssigneeNational Technology & Engineering Solutions of Sandia, LLC
InventorKurt O. Wessendorf
Life of this patent
Estimating the term…
Abstract
Various technologies pertaining to a high-impedance current source are described herein. The current source outputs a substantially constant current by way of a first transistor that draws current from a supply. The current source is configured to feed back noise from the supply to a feedback resistor at an input of an operational amplifier (op-amp) by way of a second transistor. The feedback resistor and the op-amp are configured such that responsive to receiving the supply noise feedback, the op-amp drives a gate voltage of the first transistor to cause the first transistor to reject the supply noise and cause the output of the current source to remain substantially constant.
Claims18
A current source configured to output a substantially constant current, comprising:
- an operational amplifier (op-amp);
- a feedback resistor connected to an input of the op-amp and a ground reference node;
- a first transistor that sources current from a supply, wherein a source or a drain of the first transistor is an output terminal of the current source;
- a second transistor configured to feed-back supply noise to the feedback resistor, wherein responsive to the second transistor feeding back the supply noise to the feedback resistor, the op-amp outputs the supply noise to a gate of the first transistor;
- a second resistor connected to the output of the op-amp;
- and
- a capacitor connected to the second resistor and the ground reference node, wherein an operational bandwidth of the current source is based upon a resistance value of the second resistor and a capacitance value of the capacitor.
A current source, comprising:
- an operational amplifier (op-amp);
- a control voltage source connected to a first input of the op-amp and a ground reference node;
- a feedback resistor connected to a second input of the op-amp and the ground reference node;
- a first transistor, wherein a gate of the first transistor is connected to an output of the op-amp and a source of the first transistor is connected to a voltage supply, wherein a drain of the first transistor is an output terminal of the current source;
- a second transistor, wherein a gate of the second transistor is connected to the output of the op-amp, a source of the second transistor is connected to the voltage supply, and a drain of the second transistor is connected to the second input of the op-amp, wherein the current source outputs a substantially constant current by way of the drain of the first transistor;
- and
- wherein the current source outputs the substantially constant current based upon a resistance value of the feedback resistor and a voltage output of the control voltage source.
A current source, comprising:
- an operational amplifier (op-amp);
- a control voltage source connected to a first input of the op-amp and a ground reference node;
- a feedback resistor connected to a second input of the op-amp and the ground reference node, a value of current output by the current source based upon the control voltage source and the resistor;
- a first transistor, wherein a gate of the first transistor is connected to an output of the op-amp, and wherein a drain of the first transistor is an output terminal of the current source;
- a second transistor, wherein a gate of the second transistor and a drain of the second transistor are both connected to a source of the first transistor, the source of the second transistor connected to a voltage supply;
- and
- a third transistor forming a current mirror with the second transistor, wherein a gate of the third transistor is connected to the gate of the second transistor, the drain of the third transistor connected to the second input of the op-amp, the source of the third transistor connected to the voltage supply.
Dependencies are inferred from the claim text.