varactor การใช้

• Varactor bridge op-amps started to be produced in the early 1960s.
• The classical varactor parametric oscillator oscillates when the diode's capacitance is varied periodically.
• Special-purpose variable capacitance varactor diodes are available with well-characterized wide-ranging values of capacitance.
• The classical varactor parametric oscillator consists of a semiconductor varactor diode connected to a resonant circuit or cavity resonator.
• The classical varactor parametric oscillator consists of a semiconductor varactor diode connected to a resonant circuit or cavity resonator.
• Changing the DC voltage across the varactor changes its capacitance, which changes the resonant frequency of the tuned circuit.
• The electronic button rack controlling the new electronic varactor tuner was popular in television sets of the 1970s and 1980s.
• Radio frequency VCOs are usually made by adding a varactor diode to the tuned circuit or resonator in an oscillator circuit.
• The figure shows an example of a cross section of a varactor with the depletion layer formed of a p n junction.
• I just searched Google, and found a single-transistor VCO ( varactor, not crystal ) which might suit your needs.
• The voltage used to bias the varactor diodes in modern tuners is often derived from the flyback transformer ( " Line OutPut Transformer " LOPT ).
• In practice this type of frequency synthesizer cannot operate over a very wide range of frequencies, because the comparator will have a limited varactor diodes.
• A later method used a potentiometer supplying a variable voltage to varactor diodes in the local oscillator and tank circuits of front end tuner, for electronic tuning.
• In order to suppress local oscillator leakage and provide a slight amount of image rejection, a varactor and a coil provide one stage of tracking bandpass filtering.
• In this field varactor diodes are used as a voltage variable capacitor in frequency multipliers, parametric amplifiers and variable junction when reverse biased which is the source of the capacitor effect.
• Here the signal enters and then passes through a transformer, along with a varactor and related components and forms an electrically-tuned filter / matching network, the 2 meter preamplifier.
• Later electronic types utilized the varactor diode as a voltage controlled capacitance in the tuned circuit, to receive a number of preset voltages from the rack of buttons tuning the device instantly to local stations.
• Another application is when DC power needs to be fed into a transmission line, which may be necessary to power an active device connected to the line, such as a switching transistor or a varactor diode for instance.
• Modern electronic tuners also use varactor diodes as the actual tuning elements, but the voltages which change their capacitance are obtained from a digital to analog converter ( DAC ) driven by a microprocessor or phase locked loop ( PLL ) arrangement.
• A varactor, a diode with capacitance depending on applied voltage, is often used in voltage-controlled crystal oscillators, VCXO . The crystal cuts are usually AT or rarely SC, and operate in fundamental mode; the amount of available frequency deviation is inversely proportional to the square of the overtone number, so a third overtone has only one-ninth of the pullability of the fundamental mode.