A crystal oscillator is generally connected in a circuit to provide a stable frequency source. The basic configuration includes a crystal sandwiched between two capacitors in a feedback loop of an amplifier.
Here is a simplified step-by-step guide to connect a crystal oscillator in a circuit:
1. Choosing the Oscillator: For any given operation, an appropriate crystal oscillator should be chosen considering the necessary frequency range. Oscillators usually come in a cylindrical metallic package with terminals, which can be through-hole or surface mounted on the PCB.
2. Connection to Amplifier: The crystal oscillator should be connected in the feedback loop of an amplifier, most often an inverter. To be precise, one terminal of the crystal oscillator is connected directly to the output of the inverter, while the other terminal is connected to the input of the inverter.
3. Load Capacitors: The crystal is placed between two capacitors which are connected in series to ground. The value of these capacitors (also known as load capacitors, CL1 and CL2) typically ranges between 10-33 picofarads, and helps in stabilizing the overall operation and helps to start the oscillation.
4. Connection to Circuit: The node between the two capacitors is then connected to the rest of the digital circuit that requires clock signals.
5. Biasing Resistor: In some cases, an additional resistor (often called the bias resistor) might be connected in parallel to the crystal to ensure that the amplifier works in its linear region.
6. Power Supply: Provide appropriate power supply to the amplifier. Most often the power supply is in range of 3.3-5 V.
Keep in mind that while the basic configuration described above would work in most cases, different ICs might require a different setup based on their internal configuration. Therefore, it's always a good practice to check the relevant datasheets while connecting a crystal oscillator in a circuit.