An amplifier comprising a FET transistor, a bias resistor having a first terminal connected to a gate terminal of the FET transistor, a load resistor having a first terminal connected to a D terminal of the FET transistor, a DC-to-DC step-down converter with an input terminal connected to a supply voltage, and an output terminal connected to a second terminal of the load resistor, a two-pin current-to-voltage converter with a first pin connected to an S terminal of the FET transistor and a second pin connected to ground, and a comparator having a first pin connected to a positive supply voltage, a second pin connected to a negative supply voltage, a third (output) pin connected to a second terminal of the bias resistor, a fourth pin connected to a reference voltage, and a fifth pin connected to the first pin of the current-to-voltage converter.

A circuit that includes a Darlington transistor pair having an input transistor and an output transistor configured to generate an output signal at an output node in response to an input signal received through an input node is disclosed. The circuit has a feedback coupling network coupled between the output node and the input node for feeding back to the input node a portion of an amplified version of the input signal that passes through the input transistor. The circuit further includes a bias feedback network that includes a bias transistor and a resistive network that consists of only resistive elements such that no inductors and no capacitors are provided within the bias feedback network.