A low input capacitance input stage for a high voltage amplifier includes a first input transistor configured to receive a first portion of a differential input signal and provide a first portion of an output signal, and a second input transistor configured to receive a second portion of the differential input signal and provide a second portion of the output signal. The amplifier can include a degeneration stage with a bias generator circuit. The degeneration stage can include first and second degeneration transistors coupled in series. The bias generator circuit can provide respective first and second bias signals to gate terminals of the first and second degeneration transistors to control an impedance of a signal path that couples source terminals of the first and second input transistors.