Questions & Answers on Crystal Oscillators

Mar 23, 2018

The oscillation frequency of a crystal changes as temperature varies. Both TCXOs (Temperature Compensated Crystal Oscillators) and OCXOs (Oven Controlled Crystal Oscillators) are crystal oscillators who oscillation frequency does not vary as much at high temperatures or when the temperature fluctuates.Design: A TCXO uses a compensation circuit to counter/compensate for the change in output frequen...read more

What is the difference between a VCXO and a VCO?

Crystal Oscillators

Editorial Team

Mar 29, 2018

A VCO is a Voltage Controlled Oscillators i.e. it is an electronic oscillator whose oscillating/output frequency can be controlled by a DC voltage. The oscillating/output frequency of the VCO can be modified by changing the DC voltage applied to it. This DC voltage is called the control voltage. The oscillation frequency of a VCO is generated using an electronic circuit.A VCXO is a Voltage Control...read more

The Ultimate Guide to Understanding Phase Noise

Crystal Oscillators RF Basics

Robert Rutkowski

Feb 8, 2017

What is Phase Noise?To begin understanding phase noise, here are some basic definitions of Phase Noise and what is known as Jitter.Phase Noise- Thefrequency domainrepresentation of rapid, short-term, random fluctuations in thephaseof a waveform, caused by time domain instabilities (jitter).Jitter-is a method of describing the stability of anoscillator in theTime Domain. It combines all the noiseso...read more

What is Frequency Stability?

Crystal Oscillators

Editorial Team

Oct 10, 2018

Frequency stability represents the variation of output frequency of a crystal oscillator due to external conditions like temperature variation, voltage variation, output load variation, and frequency aging. Frequency stability is typically expressed in parts per million (ppm) or parts per billion (ppb) which can be represented in the form of frequency (usually in Hz).Parts per Million (ppm): 1 ppm...read more

What is a TCXO?

Crystal Oscillators

Editorial Team

Apr 10, 2018

A TCXO or a Temperature Compensated Crystal Oscillator is a crystal oscillator specially designed to operate in high-temperature environments. The oscillation frequency of a regular crystal oscillator changes/fluctuates as the temperature rises, resulting in an unstable oscillation frequency. TCXO's provide a stable oscillation frequency in high-temperature environments. To do so, they use a tempe...read more

What is Absolute Pulling Range?

Crystal Oscillators

Editorial Team

Feb 8, 2018

A VCXO is a Crystal Oscillator that varies output frequency based on an applied control voltage. The maximum variation in VCXO's output frequency over changes in control voltage under a constant supply voltage and temperature - specified in ppm - is called Pullability or Total Pulling Range.The Absolute Pulling Range is the minimum guaranteed deviation of the VCXO from the center frequency, when t...read more

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What is an OCXO?

Crystal Oscillators

Robert Rutkowski

Nov 20, 2017

OvenControlled crystal (Xtal)Oscillators, OCXOs, are used in applications where a very high degree of frequency stability is required. Sometimes these oscillators may even be referred to as temperature stabilized crystal oscillators, or just crystal ovens.Whilecrystal oscillators (3 main types)show a high degree of stability even when the outside temperature is varied over a significant range, for...read more

What is a TCVCXO?

Crystal Oscillators

Editorial Team

Apr 25, 2018

A TCVCXO is a Temperature Compensated Voltage Controlled Crystal Oscillator. Temperature compensated means that the resonant/oscillation frequency of this crystal oscillator is less affected by a rise in temperature.When compared to a regular VCXO (Voltage Controlled Crystal Oscillator), the resonant/oscillation of a TCVCXO's will deviate less as temperature rises or changes. So a TCVCXO will requ...read more

Understand the Types of Crystals Inside of Your Oscillators

Crystal Oscillators RF Basics

Robert Rutkowski

Jan 16, 2017

Comparing the differences between AT and SC crystals and their impact on oscillator performance.Inside of every quartz oscillatorissomething called a crystal blank. The crystal blank is the resonating element of the oscillatorthat when subjected to a voltage potential will begin to vibrate and oscillate at it’s "fundamental frequency.” As you can probably imagine, the way that crystal blank is man...read more

What is a VCTCXO?

Crystal Oscillators RF Basics

Editorial Team

Apr 25, 2018

A VCTCXO is a Voltage Controlled Temperature Compensated Crystal Oscillator. This is the same as a TCVCXO i.e Temperature Compensated VCXO. Click here to read about TCVCXO's.

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What is a VCXO?

Crystal Oscillators

Editorial Team

Apr 10, 2018

A VCXO is a Voltage Controlled Crystal Oscillator whose output/oscillating frequency changes when a control voltage is applied to it under a constant supply voltage. A VCXO consists of a crystal oscillator with a varactor diode and supporting circuitry. The maximum variation in VCXO's output frequency over changes in control voltage under a constant supply voltage and temperature - specified in pp...read more

What is a DCXO?

Crystal Oscillators

Editorial Team

Nov 10, 2018

Digital Controlled Crystal Oscillators (DCXOs) are crystal oscillators whose output/oscillation frequency can be controlled digitally i.e. the output frequency generation is controlled by a x-bit binary word supplied from an external source. They are usually placed in a temperature controlled housing to provide a highly accurate output signal.Since DCXOs are digital, their frequency can be control...read more

What is Aging of a Crystal Oscillator?

Crystal Oscillators

Editorial Team

Nov 10, 2018

A small change in the frequency of a quartz crystal over a period of time is called as aging. This effect is always kept in consideration whenever a crystal is used for an application.Aging in crystal oscillators is caused by two main effects:Mass-Transfer:Addition or removal of mass from the crystal due to any sort of contamination during device packaging, leads to alteration in the frequency of ...read more

What is Jitter in a Crystal Oscillator?

Crystal Oscillators

Editorial Team

Nov 10, 2018

Jitter is a method of describing the stability of an oscillator in the Time Domain. It combines all the noise sources together and shows their effect with respect to time.Let us consider a simple pulsed signal chain. Ideally, the duration of a perfectly pulsed signal at a frequency of 1 MHz, would be exactly every 1 microseconds, with an alternating edge every 500 ns (See Fig. 1 below). But in the...read more

Quartz Crystal vs LC Tank Circuit as a Resonant Element

Crystal Oscillators

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