oscillator generator

Digital potentiometers are versatile devices; you can use them in many filtering and waveform-generation applications. This Design Idea describes an oscillator in which setting the resistance of two digital potentiometers independently programs the oscillation amplitude and frequency. Figure 1 shows a typical diode-stabilized Wien-bridge oscillator that generates accurate sine waves from 10 to 200 kHz.
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Figure 1 shows a novel circuit that uses a low-cost, high-speed op amp as a crystal-controlled RF sine-wave oscillator. An op-amp oscillator offers several advantages. Because an op amp is a complete amplifier with a high-impedance input and a low-impedance output, it considerably simplifies the circuit design by replacing the traditional multiple-transistor circuit with its [...]

In addition to its normal role of controlling oscillation frequency, the crystal in Fig 1 also acts as a high-Q, self-tuned output filter, which rejects the noise and harmonics of its input voltage, VB. The result is a clean output-frequency spectrum. With an output frequency of 10.7 MHz, second harmonic distortion is -76 dBc, and [...]