| 摘要 |
A low duty cycle relaxation oscillator (12) periodically gates an ultrasonic frequency relaxation oscillator (13) into an on state. The ultrasonic frequency oscillations are supplied to an electric-compressional wave transducer (15) by way of a push-pull driver (14). The duty cycle and repetition rate of the relaxation oscillator (12) and the ultrasonic oscillation frequency are such that compressional waves derived by the transducer (15) incident on fleas in the region where the transducer (15) is located repels the fleas. All active elements in the oscillator (12,13) and driver (14) are CMOS devices which draw only leakage current while in quiescent bi-level states and through current from a battery (21) during transitions between the bi-level states. The drain from the battery (21) is reduced by connecting a high impedance (74) between the battery (21) and the CMOS devices (31,...36) during a relaxation oscillator transition. |
