Implantable nerve stimulator having internal electronics without ASIC and methods of use
An implantable pulse generator that includes a current source/sink generator is disclosed herein. The current source/sink generator includes a current drive differential amplifier. The current driver differential amplifier is configured to selectively source current to, or sink current from a target tissue. The current drive differential amplifier includes an inverting input and a non-inverting input. One of the inputs of the current drive differential amplifier is connected to a virtual ground, and the other is connected to a current command. A stimulation controller can supply a voltage to the other of the inputs of the current drive differential amplifier to select either current sourcing or current sinking.
1. An implantable neurostimulator for delivering one or more electrical pulses to a target region within a patient's body with an implantable lead comprising a plurality of electrodes positionable proximate to the target region and electrically coupleable thereto, the implantable neurostimulator comprising:
a bio-compatible housing defining a hermetically sealed internal volume configured for implantation within a body of a patient; and
circuitry disposed within the hermetically sealed internal volume of the bio-compatible housing, wherein the circuitry is configured to generate one or more electrical pulses, and wherein the circuitry comprises:
a first current control module; and
a second current control module, wherein each of the first and the second current control modules comprise:
a current command configured to supply a voltage within a first range, wherein the first range is between a minimum voltage and a maximum voltage;
a virtual ground having a ground voltage;
a current drive differential amplifier having a non-inverting input coupled to the current command, an inverting input coupled to the virtual ground, and an output, wherein the current drive differential amplifier is configurable as a source or as a sink based on a relative voltage supplied by the current command with respect to the ground voltage; and
a load path selectively coupling the output of the current drive differential amplifier to the lead, wherein the load path comprises a sensing resistor located between the output of the current drive differential amplifier and the lead.
2. The implantable neurostimulator of claim 1 , wherein the ground voltage is an intermediate voltage between the minimum voltage and the maximum voltage.
3. The implantable neurostimulator of claim 2 , wherein at least one of the first and second current control modules comprises a current sense differential amplifier comprising a sense non-inverting input, a sense inverting input, and a sense output.
4. The implantable neurostimulator of claim 3 , wherein the sense non-inverting input is connected via a first resistor having a first resistance to the load path between the sensing resistor and the output of the current drive differential amplifier, and wherein the sense inverting input is connected via a second resistor having the first resistance to the load path between the sensing resistor and the lead.
5. The implantable neurostimulator of claim 4 , wherein the sense non-inverting input is connected to the virtual ground via a third resistor having a second resistance, and wherein the sense inverting input is connected to the sense output via a fourth resistor having the second resistance.
6. The implantable neurostimulator of claim 5 , wherein the inverting input of the current drive differential amplifier is connected to the sense output, wherein the sense output has a voltage equal to a sum of the ground voltage and a voltage drop across the sensing resistor.
7. The implantable neurostimulator of claim 5 , further comprising a voltage sensor configured to measure a voltage drop across the sensing resistor based on the output of the current sense differential amplifier.
8. The implantable neurostimulator of claim 7 , wherein the voltage drop across the sensing resistor is measured by determining a difference between the ground voltage and the output of the current sense differential amplifier.
9. The implantable neurostimulator of claim 8 , wherein the first current control module is configured to selectively source current to the lead and to selectively sink current from the lead, and wherein the second current control module is configured to selectively source current to the lead and to selectively sink current from the lead.
10. The implantable neurostimulator of claim 8 , wherein the voltage at the inverting input of the current drive differential amplifier is equal to the ground voltage of the virtual ground when at least one of the first current control module and the second current control module is operating at a steady state.
11. The implantable neurostimulator of claim 10 , wherein the current drive differential amplifier is configurable for current sourcing when the supplied voltage applied to the non-inverting input of the current drive differential amplifier is greater than the ground voltage of the virtual ground.
12. The implantable neurostimulator of claim 11 , wherein the current drive differential amplifier is configurable for current sinking when the supplied voltage applied to the non-inverting input of the current drive differential amplifier is less than the ground voltage of the virtual ground.
13. The implantable neurostimulator of claim 1 , wherein the load path selectively couples the output of the current drive differential amplifier to the lead via one of an anodic switch array and a cathodic switch array, wherein the anodic switch array and cathodic switch array are controllable by a switch controller, and wherein the sensing resistor is located between the output of the current drive differential amplifier and the one of the anodic switch array and the cathodic switch array.