The difference between the self drive and external drive buzzers
Depend on the driving signal, the buzzer divide into self drive and external drive. However inner circuit/ no circuit, DC/ AC, and active/ passive are all mean the same.

The design of the self drive buzzer is to set the circuit inside the buzzer and just offer the direct current to work. The inner circuit has the designed frequency and voltage for the buzzer to generate sound, therefore the frequency of the self drive buzzer is fixed. However the frequency is still different from each buzzer, normally is 2300Hz, the acceptable range is +/-300Hz.

However, the external drive buzzer needs to be drove by the signal of 1/2 square wave V 0-p (Magnetic type), or square wave V p-p (Piezo buzzer)

It is convenient to use a self drive buzzer, but the disadvantages are the higher cost, the higher defective rate and the unchangeable frequency.

The comparison between self and external drive buzzer: