An electronic circuit for generating a trapezoidal excitation waveform includes a controllable frequency source and a trapezoidal waveform generator. The controllable frequency source generates a source waveform that, upon energization thereof, has an initial frequency value, and decreases in frequency to a substantially constant frequency value a time period after energization. The trapezoidal waveform generator receives the source waveform and, in response, generates a trapezoidal waveform at least when the source waveform frequency attains the substantially constant frequency value.