Examples provide for a self-test circuit. The self-test circuit comprises input circuitry; testing circuitry; and a circuit to be tested, coupled between the input and testing circuitry and comprising at least a piezoelectric crystal. The input circuitry is configured to generate and transfer a predefined electric signal comprising at least a sinusoidal signal through at least the piezoelectric crystal of the circuit to be tested to generate an output signal. The testing circuitry is configured to analyze the output signal.