Apparatus and methods for reducing output noise of a signal channel

A method of reducing output noise of a signal channel, the method comprising:

• biasing an amplifier with a bias current generated from a voltage-controlled current source;
• controlling a magnitude of the bias current based at least partly on a voltage across a biasing capacitor;
• sampling a bias voltage onto the biasing capacitor and holding the voltage across the biasing capacitor substantially constant between a first time instance and a second time instance;
• amplifying an input signal to generate an amplified signal using the amplifier;
• sampling the amplified signal at the first time instance to generate a first sample;
• sampling the amplified signal at the second time instance to generate a second sample;
• and
• generating an output signal based on a difference between the first sample and the second sample.

An apparatus, comprising:

• an amplifier configured to amplify an input signal to generate an amplified signal, wherein the amplifier comprises a means for biasing including a biasing capacitor and a voltage-controlled current source for generating a bias current, wherein the biasing means is configured to control a magnitude of the bias current of the amplifier based at least partly on a voltage across the biasing capacitor;
• and
• a means for sampling the amplified signal generated by the amplifier, wherein the sampling means is configured to generate an output signal based on a difference between a first sample of the amplified signal taken at a first time instance and a second sample of the amplified signal taken at a second time instance after the first time instance,
• wherein the biasing means is configured to sample a bias voltage onto the biasing capacitor before the first time instance, and wherein the biasing means is configured to hold the voltage across the biasing capacitor substantially constant between the first time instance and the second time instance.