Low noise amplifier

Abstract

The invention teaches an amplifier () with an input signal (IN) coupled to the gate of a second transistor (Q) and an output signal (OUT) coupled to an output node between a third resistor (R) and the drain of the second transistor (Q). A third transistor (Q) is coupled in parallel between the output node and the gate of a second transistor (Q). A first bias signal (Vbias) is coupled to the output node and the gate of the third transistor (Q). The amplifier preferably also includes a plurality of switchable resistors coupled to the output node to adjust the output for process variations. The invention also describes a method of compensating for process variations in an output of an amplifier which comprises producing a reference signal dependent on the difference between a reference value and an actual value and switching one or more resistors into the output of the amplifier to adjust the output of the amplifier to reflect the process variations. The reference signal is produced by comparing the differential inputs of a reference input produced from a reference potential across a first resistorhaving a reference value in series with a constant current sourceand an actual input produced from an actual potential across a second resistorhaving substantially the same reference value. The second resistoris in series with the channel of a transistor