In an oscillator circuit where positive feedback is obtained through a single capacitor in series with the crystal, the type of oscillator is:

The Pierce oscillator is a popular crystal oscillator design known for its simplicity and excellent frequency stability. In this configuration, the quartz crystal is placed in the feedback path, often in series with a single capacitor that can be adjusted to slightly 'pull' or fine-tune the exact operating frequency. By contrast, a Colpitts oscillator uses a capacitive voltage divider for feedback, and a Hartley oscillator uses a tapped inductor. The Miller oscillator typically places the crystal at the input and relies on internal device capacitance for feedback rather than a distinct series capacitor.