| 摘要 |
<p>The amplifier has a saw-tooth signal generator with an operational amplifier, the amplitude of the saw-tooth signal depending on the ratio of resistors and the frequency on a resistor and a capacitor. The saw-tooth signal is applied to one input of a comparator, the low-frequency signal being applied to the other input. The output from the comparator is a rectangularly modulated signal whose cyclic ratio is a function of the low-frequency signal. The signal is fed via power amplifying stages to a loudspeaker. Thus, a low-frequency wave having the usual mixture of waves of continuously variable amplitudes and frequencies is transformed into a square wave of ultrasonic frequency, whose instantaneous cyclic ratio is linearly bound to the instantaneous value of the incident signal.</p> |
