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a wide variety of discrete quartz crystal elements from 1MHz to 200MHz.
Crystal products can be housed into different packages – through hole and
surface mount. GED can provide quartz thickness monitor crystals.
manufactures 14-pin DIP, 8-pin DIP, surface mount -9x14mm ceramic package
and 5x7mm ceramic package in all logic levels.
GED designed a very low
frequency oscillator from 50Hz to 2MHz HCMOS/TTL output.
Quartz Oscillator is a circuit using an active element for example-
transistor or an IC,
quartz crystal and passive devices so
arranged and configured so as to create a positive feedback through the
crystal to cause it to oscillate. The oscillations of the crystal create a
frequency that is in the case of AT cut crystal dependent upon the crystal
thickness . The active elements determine to a great degree the output logic
level which could be TTL, CMOS, ECL.
GED offers VCXOs in a wide
variety of packages
–14 pin DIP and 8-pin DIP thru-hole and surface mount ceramic packages in
9x14mm and 5x7mm.
Voltage Controlled Crystal Oscillator (VCXO) is a crystal
oscillator whose frequency can be tuned by a control voltage on one of the
oscillator package pins as designated. This voltage can be used to modulate
the frequency up to a predetermined rate depending on specification. Typical
control voltages can vary from 0-3V or 0-5V.
Compensated Crystal Oscillator (TCXO) is a crystal control oscillator whose
frequency is maintained to a very high degree of accuracy over the temp
range specify by the customer typically –20 to 70C and with stabilities down
to typically 1-3ppm. The freq of the crystal is held relatively constant by
the changing of capacitance in the crystal path over temp. As the crystal
frequency increases the capacitance compensation circuit will bring it
towards zero PPM and conversely as the frequency decreases the capacitance
compensation circuit will again bring it towards zero PPM.
Controlled Crystal oscillator (OCXO) is used where extremely small
variations of frequency are required typically below 0.5ppm over specified
temp range typically -20°C to 70°C. The frequency of the oscillator is
stabilize by a heating circuit that will elevate the temp of the crystal and
other critical elements to a temperature higher than the highest specified
temperature by approx 10 –15 deg i.e. an oscillator to operate at 0-70°C
will have a heating circuit that will maintain the constant temp at 80-85C.
Control Oscillator (VCO) Is an oscillator used to generate a frequency
using an LC circuit rather than a quartz crystal so as to be able to have an
extended pull range typically 5-10% of the center frequency. Frequency range
of VCOs could start from as low as 10MHz and extend through the Gigahertz
VCOs find wide application in
wireless communication systems for tracking frequencies over a wider
spectrum range than cannot be otherwise captured by a VCXO.