Patent US 5,459,434

A detector amplifier includes a first stage, a second stage and a low voltage supply. The first stage has a first input for receiving a first input signal, and an output for outputting a first output signal, and amplifies and/or demodulates the first input signal to form the first output signal. The second stage is coupled in series to the first stage and has a first input for receiving the first output signal, a second input for receiving a second input signal, and an output for outputting a second output signal. The second stage amplifies and/or demodulates the first output signal and the second input signal to form the second output signal. The low-voltage supply is coupled in series with the first and the second stage for supplying a DC current to the stages.