Since the operating current of the buzzer is generally quite large, it is impossible for the I/O port of the single-chip microcontroller to directly drive it* (but the AVR can drive small-power buzzers), so an amplification circuit is needed for driving. Generally, a transistor is used to amplify the current. The buzzer driving circuit usually consists of the following parts: a transistor, a buzzer, a rectifier diode and a power filter capacitor. 

1. Buzzer

The sound-producing component can produce sound by applying a direct current voltage (for active buzzers) or a square wave (for passive buzzers) across its two ends. Its main parameters include size and shape, sound emission direction, operating voltage, operating frequency, operating current, and driving mode (direct current/square wave), etc. These can all be selected according to the requirements. 

2. Continuation Diode 

The buzzer is essentially a sensitive component. Its current cannot change abruptly, so a diode for continuous current flow must be provided. Otherwise, a peak voltage of several tens of volts will be generated across the buzzer, which may damage the driving transistor and interfere with other parts of the entire circuit system. 

3. Filter capacitor 

The function of the filter capacitor C1 is to filter out the influence of the buzzer current on other parts. It can also improve the AC impedance of the power supply. If possible, a 220uF electrolytic capacitor can be connected in parallel. 

4. Triode

Transistor Q1 functions as a switch. When the base of the transistor receives a high level signal, it becomes fully conductive and causes the buzzer to sound; while a low level signal at the base causes the transistor to turn off, and the buzzer stops sounding.