Square wave signal generating circuit

The utility model discloses a square wave signal generating circuit. The square wave signal generating circuit comprises a power supply circuit, an oscillating circuit, a voltage follow circuit and a voltage comparison circuit which are connected orderly. The oscillating circuit comprises a high frequency amplification transistor Q1 of which the base and the collector are connected with the output end of the power supply circuit via a resistor R11 and a resistor R13 respectively, and the base and the emitter are grounded via a resistor R12 and a resistor R14 respectively. An adjustable capacitor C13, a capacitor C14 and an inductor L2 form a parallel resonance circuit, the adjustable capacitor C13 is connected between the collector of the transistor Q1 and the ground, and the inductor L2 and the capacitor C14 are connected in series between the collector of the transistor Q1 and the ground. The common end of the inductor L2 and the capacitor C14 is connected with the base of the transistor Q1 via a capacitor C11, and the collector of the transistor Q1 is connected with the input end of the voltage follow circuit. The square wave signal generating circuit of the utility model can adjust the frequency of an outputted square wave signal by changing the capacitance value of the adjustable capacitor, and has the advantages of being simple in circuit structure and lower in cost, and being easy to realize.