In an LC oscillator, the frequency of oscillator is ___________ L or C.
A. Proportional to square of
B. Directly proportional to
C. Independent of the values of
D. Inversely proportional to square root of
Crystal oscillators are available in a wide frequency range, from as low as 0. MHz to over MHz, catering to diverse applications like timekeeping, communication, and advanced electronic systems.
The resonant frequency of crystal oscillators is highly stable, attributed to physical dimensions of the crystal. Special types like TCXOs and OCXOs offer enhanced stability across temperature variations.
Crystal oscillator datasheets often indicate a range like "10-50 MHz," signifying the variety of distinct frequencies available within a product family. Each crystal also comes with a specified frequency tolerance, indicating the performance range of each unit.
Quartz crystals come in a large variety of frequencies within the crystal oscillator frequency range.
The concept of crystal oscillator frequency range can encompass several aspects. Firstly, manufacturers produce crystal oscillators within specific frequency ranges, offering a variety of similar functioning crystals each with a different nominal frequency. Secondly, the collective frequency range of all manufactured crystal oscillators spans an extensive spectrum, starting as low as 0. MHz and reaching upwards of MHz and beyond. Read on as we&#;ll be discussing crystal oscillator frequency ranges.
Frequency Range
Specific Frequencies
Common Applications
Low (32 kHz to 1 MHz)
32.768 kHz
Quartz wristwatches, Real-time clock modules
100 kHz to 1 MHz
RFID systems, Consumer electronics
Intermediate (1 to 10 MHz)
4 to 8 MHz
Microcontrollers, TV remote controls
10 MHz
Digital circuits, Communication devices
High (10 to 100 MHz)
20 to 40 MHz
Microprocessors, Wireless devices
100 MHz
Fast digital circuits, High-speed ADCs
Very High (Above 100 MHz)
125 to 200 MHz
Advanced communication systems, Ethernet
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Above 200 MHz
Radar systems, Satellite communication
A crystal oscillator's nominal frequency is its designed resonating frequency &#;the frequency it's intended to operate at. For example, an oscillator marked for 10 MHz operates at this nominal frequency. However, oscillators in practical scenarios exhibit some frequency deviations. These deviations are measured by the frequency stability, typically noted in the product's datasheet.
The resonant frequency of a crystal oscillator is remarkably stable, largely due to its dependence on the crystal's physical dimensions. This stability, typically measured in parts per million (ppm), far surpasses the less stable resonant frequencies of RC or LC oscillators. Standard resonant frequencies for crystals are available across a wide spectrum, catering to various application requirements we discuss below.
The frequency of a crystal can vary with its temperature, as the crystal's size is dependent on temperature. To mitigate this, temperature-compensated crystal oscillators (TCXOs) and oven-controlled crystal oscillators (OCXOs) are used in applications requiring high-frequency stability across a range of temperatures. Nonetheless, in crystals that are oriented in specific ways, known as cuts, these variations can be minimized so that they are virtually insignificant for most applications, except those that require extremely precise measurements.
By employing frequency dividers, frequency multipliers, and phase-locked loop circuits, it becomes feasible to generate a broad spectrum of frequencies from a single reference frequency.
Examining a datasheet of a crystal oscillator may show the crystal oscillator frequency range as "10-50 MHz." It is important to note that this doesn&#;t indicate the frequency range of a single crystal product but rather the production of various crystals within the family, each with distinct frequencies in the spectrum. So, a crystal operating at 20 MHz is an entirely separate product from one operating at 25 MHz.
Additionally, these crystals come with a specified frequency tolerance, denoting the performance range of each unit. Therefore, purchasing multiple 25 MHz crystals with a tolerance of 20 ppm guarantees that their frequencies will lie between 24. MHz and 25. MHz.
Lower-frequency crystals are commonly used in applications, including real-time clocks, quartz watches, and various clock devices. On the other hand, higher frequency crystals are predominantly used for electronic communication, such as cellular devices, remote controls, GPS systems, radios, and modems. There are, of course, exceptions where some high-frequency crystals are also utilized in clock mechanisms, while low-frequency crystals find their use in electronic communication technologies.
In certain specialized uses, crystal oscillators are tailored for specific frequencies. For instance, a 4. MHz oscillator is perfect for timers because dividing this frequency by 222 yields a precise 1 Hz signal, thanks to a 22-stage binary divider. Below, we&#;ve summarized a variety of trends within the vast crystal oscillator frequency range.
Crystal Oscillator Frequency Trends
Application Category
Frequencies
Purpose/Significance
Timekeeping and Real-time Clock (RTC)
0. MHz, 0. MHz
Used for real-time clocks and quartz watches, typically in lower frequency ranges.
Data Communication and UART
1. MHz, 3. MHz
Used in UART applications for serial communication, facilitating standard baud rates.
Audio/Video (A/V)
2. MHz, 3. MHz
Employed in CD-DA systems and NTSC color subcarriers, aligning with specific signal frequencies.
Radio and Intermediate Frequency (IF) Filters
4.5 MHz, 10.7 MHz
Common in radio applications, such as IF filters in FM broadcasting.
Binary Division
Variable
Frequencies allowing binary division to 1 Hz or 32.768 kHz, crucial for digital systems and microcontrollers.
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