Ultrasonic atomizer unit utilizing shielded and grounded elements

In an ultrasonic atomizer unit including a chamber base, a piezo-electric vibrator attached to the chamber base, and a driving circuit for energizing the piezo-electric vibrator, the improvement wherein said driving circuit is separated into an oscillator part and a power supply part having a rectifier, said oscillator part is shielded by a metal housing, one of the power supply lines to said oscillator part extends through an aperture in said metal housing and is coupled to said rectifier, and another power supply line to said oscillator part is connected to said metal housing and also is coupled to said rectifier, there is provided a variable circuit element for controlling the output signal from said oscillator part, said variable circuit element is positioned outside said metal housing, a filter circuit is inserted between said oscillator part and said variable circuit element, said oscillator part comprises a self-driving oscillator circuit, said variable circuit element is a variable resistor, said variable resistor and said filter circuit are arranged in an electrode biasing circuit of said oscillator circuit, said oscillator circuit includes a transistor having a grounded collector, and said variable resistor is coupled to the base of said transistor by said filter circuit.