Oscillators Glossary

  • Center Frequency

    A specified reference frequency of the crystal typically denoted in megahertz (MHz) or kilohertz (kHz).

  • CMOS

    Abbreviation for "Complementary Metal Oxide Semiconductor."

  • Control Voltage

    Range of voltage used to pull the frequency.

  • Duty Cycle

    Measurement of output waveform's uniformity; also referred to as symmetry. Measurement of the time in which, the output waveform is in a logic high state, expressed in percentages (%). Must be measured at a specified voltage or at a percentage of the output waveform amplitude.

  • ECL

    Abbreviation for "Emitter Coupled Logic."

  • Enable/Disable Function

    Control function which, enables or disables the output of the oscillator. When the oscillator is in its disabled state, the oscillator is still operating, but no output is coming from the output pin.

  • Enable/Disable

    Time Time between application of the proper voltage to the enable/disable pin

  • Fall Time

    Amount of time it takes the output voltage to go from Logic '1' to logic '0'.

  • Input Current

    Amount of current consumption by an oscillator from the power supply, typically specified in milliamps (mA).

  • Linearity

    Uniformity of the shift in frequency over voltage change, when pulling frequency of a VCXO.

  • Load Drive Capability (Fan Out)

    Maximum load the oscillator can drive. Specified in terms of the number of gates or type of load circuit.

  • Load Impedance

    Impedance presented by a load connected to a generator or any other source

  • Logic Levels

    Defined as the Output Voltage Logic High or "Logic 1" and the Output Voltage Logic Low or "Logic 0"

  • Oscillator

    A circuit that produces an alternating current of a specific frequency at its output terminals

  • Output Current

    Represented by IOL and IOH; it is the output current at VOL and VOH.

  • Output Load (Fan out)

    Capability of the oscillator to drive other devices. TTL devices are specified in the number of gates that can be driven; i.e., 10 TTL gates. CMOS outputs are specified in pF, i.e., 15pF or 50pF loads.

  • Output Voltage

    Represented by VOL; it is the maximum voltage that output low will be and VOH is the minimum voltage that output high will be.

  • Overlap Time

    Time measured at 50% Vp-p, where the two outputs of a complementary output ECL oscillator overlap.

  • Pin Through

    Only applies to packages with leads. When the device is mounted on a PCB, the leads go through the board.

  • Pullability

    Amount the frequency that can deviate by varying the voltage on the control pin.

  • Rise Time

    Amount of time it takes the output voltage to go from Logic '0' to logic '1'.

  • Sine wave

    Periodic wave which, is represented by a sine curve. The amplitude of such wave is a function of the sine of a linear quantity such as phase or time.

  • Square Wave

    An alternating or pulsating current or voltage whose wave shape is square.

  • Stability

    Maximum amount of frequency deviation of the oscillator; which, includes the tolerance at 25°C; drift over operating temperature range; changes in input voltage; changes in load, shock, vibration; and aging.

  • Standby Current

    Amount of current consumed by the oscillator when it is in a standby mode.

  • Standby Function

    A control function like the Enable/Disable function. In this case, the oscillator actually stops oscillating. This type of oscillator draws less current than an Enable/Disable type oscillator (when both are in their disabled states).

  • Start-up Time

    Period from the instant when a voltage is applied to the oscillator until the oscillator output is stabilized.

  • Supply Voltage

    Voltage required for the oscillator to operate within specification.

  • Surface Mount

    Describes a package with pads that mount to the surface of the PCB.

  • Symmetry

    Measurement of the uniformity of the output waveform

  • T.C.X.O

    Abbreviation for "Temperature Compensated Crystal Oscillator." This type of oscillator contains a temperature sensing network that adjusts the output frequency, thereby allowing the frequency to remain constant over a specified temperature range. Very often referred to as precision oscillator.

  • Tri-State Output

    The ability to turn the output on or off using pin # 1 for control. The output will go to high impedance when disabled, which facilitates the use of Auto Test Equipment (ATE). Tri-state can be substituted for non-tri-state if pin #1 is left open or held high.

  • TTL

    Abbreviation for "Transistor-Transistor Logic."

  • V.C.X.O

    Abbreviation for "Voltage Controlled Crystal Oscillator." This type of oscillator contains a network that employs changes in voltage to change the output frequency.

  • Warm Up

    Time required for an oscillator's frequency to settle within a given tolerance of the frequency after several hours.