A circuit arrangement and method utilize a variable threshold, multi-stage pulse shaping circuit to pulse shape a signal output by a crystal oscillator circuit. Each stage of the pulse shaping circuit includes a Schmitt trigger that drives an input of a latch, and that has a programmable trip point controlled to reject distorted pulses generated by the crystal oscillator circuit. A variable threshold, multi-stage pulse shaping circuit may be used, for example, to generate a clock signal for an electronic circuit that is more resistant to noise and other environmental effects, thereby reducing the likelihood of clock-related errors in the electronic circuit.