Sinusoidal Burst Generator for Auditory Evoked Response Research

A simple stimulator has been devised in which sinusoidal signals in the audio range are linearly modulated to generate tone bursts of controlled duration and shape for auditory research. The stimulator comprises a transistor differential pair modulator whose differential collector voltage is the product of the voltage applied at a base (sine wave input) and the emitter current (varied by the modulating waveform). A trapezoidal generator is provided for the modulating waveform. The output is greater than 60 dB above noise and switching transients and the ON-OFF ratio is greater than 60 dB up to 50 kHz. The frequency response is flat to 50 kHz, and there is no appreciable distortion. The trapezoidal generator has equal rise and fall times which are independent of the flat-top duration.