Low noise low current bias amplifier topology

A circuit comprising:

• a controlling amplifier configured to produce an amplified signal from an input signal, the controlling amplifier comprising a first controlling amplifier input terminal configured to receive the input signal, a second controlling amplifier input terminal coupled to a zero current node, and a controlling amplifier output terminal configured to output the amplified signal, wherein the controlling amplifier comprises a bipolar amplifier;
• a zero current circuit coupled to the zero current node, the zero current circuit configured to force voltages across each at least one capacitor to zero, the zero current circuit comprising:
• at least one capacitor comprising a first terminal coupled to the zero current node,
• at least one resistor comprising a first terminal coupled to the zero current node, and
• a zero current circuit amplifier comprising a zero current circuit amplifier output coupled to a second terminal of the at least one resistor and configured to present zero volts across a series combination of the at least one resistor and the at least one capacitor, wherein the zero current circuit amplifier comprises a field effect transistor amplifier, and wherein a resistance of the at least one resistor and a capacitance of the at least one capacitor are selected to provide a current path away from the zero current node through the at least one resistor for at least one frequency of the input signal;
• and
• a servo amplifier circuit comprising:
• a servo amplifier and a feedback, the servo amplifier comprising a first servo amplifier input terminal coupled to the controlling amplifier output terminal, a second servo amplifier input terminal, and a servo amplifier output terminal, wherein the servo amplifier comprises a field effect transistor amplifier, and wherein the feedback is coupled to the second servo amplifier input terminal and the servo amplifier output terminal,
• a nesting servo amplifier and a second feedback, the nesting servo amplifier comprising a first nesting servo amplifier input terminal coupled to the servo amplifier output terminal, a second nesting servo amplifier input terminal, and a nesting servo amplifier output terminal, wherein the nesting servo amplifier comprises a field effect transistor amplifier, and wherein the second feedback is coupled to the second nesting servo amplifier input terminal and the nesting servo amplifier output terminal, and
• an additional nesting servo amplifier and a third feedback, the additional nesting servo amplifier comprising a first additional nesting servo amplifier input terminal coupled to the nesting servo amplifier output terminal, a second additional nesting servo amplifier input terminal, and an additional nesting servo amplifier output terminal, wherein the additional nesting servo amplifier comprises a field effect transistor amplifier, and wherein the third feedback is coupled to the second additional nesting servo amplifier input terminal and the additional nesting servo amplifier output terminal,
• wherein the servo amplifier operates at a first frequency, the nesting servo amplifier operates at a second frequency lower than the first frequency, and the additional nesting servo amplifier operates at a third frequency lower than the second frequency.