How To Change Hvac Capacitor Storables

What is a crystal oscillator?

Crystal oscillators are recognizable from their LC oscillator counterparts . For the Pierce and Colpitts oscillators, the crystal replaces the inductor in the corresponding LC tuned circuit oscillators. Not sur-prisingly, the crystal will appear inductive in the circuit.

How do you adjust the capacitance of an oscillator?

The capacitance value is adjusted by the 4 last bits (3:0) of the 'FREQTUNE' register. The default value of the register is 0x0F which corresponds to no added capacitance. For each decrement in the register value, extra capacitance is added to the oscillator circuit, reducing the oscillator frequency.

How resonant crystals are used in oscillator circuits?

This tells the crystal manufacturer how the crystal will be used in the oscillator circuit. Series resonant crys-tals are used in oscillator circuits that contain no reac-tive components in the feedback loop. Parallel resonant crystals are used in oscillator circuits that con-tain reactive components.

What is the nominal load capacitance of the XTAL oscillator?

For example, if the nominal load capacitance of the XTAL defined by the manufacturer is 10 pF, then the PCB design and the selection of all external components should ideally be done in such way that the overall capacitance connected to the XTAL equals 10 pF. See the “capacitive” Pierce oscillator model in Figure 4.

How does a Pierce crystal oscillator oscillate?

We shall see for the Pierce and Colpitts crystal oscillators, the crystal will appear inductive in the circuit in order to oscillate. The Pierce crystal oscillator (Figure 13) is a series res-onant circuit for Fundamental mode crystals. It oscil-lates just above the series resonant frequency of the crystal .

What are the components of an oscillator circuit?

The oscillator circuit consists of an inverting amplifier (normally a regular inverter), a feedback resistor, two capacitors and a crystal. The first two components are internal in the IC while the capacitors and the crystal are external and must be selected for each separate design.