Cathode follower oscillator
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The Cathode follower oscillator is an electronic oscillator circuit in which the oscillation frequency is determined by a tuned circuit consisting of capacitors and inductors, that is, an LC oscillator.[1] The circuit is also known as differential amplifier oscillator, emitter follower oscillator , source-coupled oscillator or Peltz oscillator.[2][3] This oscillator uses one connection to get a signal from the LC-circuit and feeds an amplified signal back. The amplifier is a long-tail pair of two triodes, two bipolar transistors or two junction FETs.
Operation
In the Cathode follower oscillator schematic, the long tail amplifier is connected to a tap of the LC-circuit inductance for a light load on the LC-circuit. A grid-leak couples the grid of the left triode to the LC-circuit. The left triode uses common anode circuit which has high input impedance, low output impedance and no voltage amplification. The long-tail resistor couples the two triodes. The right triode uses common grid circuit which has low input impedance, high output impedance and no current amplification. A capacitor at the anode resistor of the right triode couples the amplified signal back to the LC-circuit. At low frequency, both triodes have a phase shift of zero degree.
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- ^ Jiri Vackar, LC Oscillators and their Frequency Stability, Fig. 7, Tesla Technical Reports, Praha, December 1949
- ^ Günter Peltz, Zweipolige Oszillatorschaltungen für Parallel- und Serienresonanz, Funkschau, 1971, Heft 15, S. 465–466
- ^ Koster, Waldow, Wolff, A unique, low-voltage, source-coupled J-FET VCO, RF signal processing, April 2001