Inside an IC there is an inverting amplifier (phase shift ca. 180°) forming part of the
oscillator circuit. The external circuitry consists of quartz crystal, Cx1, Cx2 und Rv and
another phase shift of ca. 180°, to fulfill the feedback requirements of 360° (or 0°) and
enable the circuit to oscillate with the frequency given by the quartz crystal.For applications: chip cards, mobile communication, medical etc.