A ONE TRANSISTOR FM TRANSMITTER
The 2N2222 phase-shift oscillator circuit is a versatile design commonly used in RF applications. It consists of three stages of phase-shifting, typically implemented using RC networks. Each stage contributes to a total phase shift of 180 degrees, with an additional 180 degrees provided by the transistor, allowing for sustained oscillations at the desired frequency.
In this configuration, the 2N2222 transistor operates in the common-emitter mode, where the input signal is applied to the base terminal. The output is taken from the collector, where the sine wave oscillation is generated. The frequency of oscillation is primarily determined by the resistor and capacitor values in the RC networks. For a 1,000 Hz output, careful selection of these components is crucial.
The TCG-610 varactor diode plays a significant role in frequency modulation. By varying the reverse voltage applied to the varactor, the effective capacitance changes, which in turn alters the resonant frequency of the tank circuit. This modulation allows for dynamic frequency adjustments, making the circuit suitable for applications requiring frequency agility.
The inclusion of a 1,000-ohm potentiometer in the collector circuit provides a means to fine-tune the amplitude of the output signal. By adjusting this potentiometer, the user can control the collector current, thereby influencing the overall gain and stability of the oscillator.
Overall, this circuit exemplifies a practical implementation of a phase-shift oscillator using a 2N2222 transistor and a varactor diode, showcasing its functionality in generating a stable sine wave output while allowing for frequency modulation through capacitance variation.The 2N2222 circuitry is a three-element, phase-shift oscillator circuit, designed to yield a 1,000-Hz sine wave. The 1,000-Hz sine wave is then applied to the TCG-610 varactor diode, 6 pF at 4 V, which changes the tank capacitance, thus varying the rf oscillator frequency at a 1,000-Hz rate.
The 1,000-? potentiometer in the collector circuit can be adjusted.. 🔗 External reference
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