Various embodiments of an input protection circuitry may be configured with a variable tripping threshold and low parasitic elements, which may prevent a signal from propagating into the protected equipment/device if the voltage of the input signal exceeds a certain limit. The input protection circuit may operate to protect a measurement instrument, which may be an oscilloscope, early in the signal path leading into to the instrument, to avoid exposing sensitive circuitry to damaging voltage levels, and without introducing significant parasitic elements that would degrade the performance of the instrument. The protection circuit may be configured to include clamping to provide protection during the circuit response delay time. The input protection threshold of the protection circuit may be adaptive to a selected voltage range on the instrument without trading-off instrument performance and features.