Non-sinusoidal wave generation circuits are similar in function to sinusoidal oscillation circuits, as both are designed to produce signals with specific frequencies and amplitudes. Therefore, they share common performance metrics such as frequency stability, amplitude consistency, and waveform quality, with frequency being the most critical factor. As a result, non-sinusoidal oscillation circuits also require tuning of frequency, amplitude, and waveform. Since the signal is non-sinusoidal, an oscilloscope is typically used for measurement, while a digital frequency meter can be used to measure frequency directly. Although the adjustment and testing methods for non-sinusoidal circuits are largely similar to those of sine wave circuits, there are some key differences that are worth noting.
1. Amplitude Adjustment: Non-sinusoidal circuits are primarily used to generate square or triangular waves, where components operate in a highly nonlinear region, producing only high and low-level outputs. The amplitude of these signals is not determined by loop gain but rather by the combination of current, voltage, and supply voltage when the device enters a strong nonlinear state. To achieve stable and precise amplitude, high-precision voltage regulators are commonly used to control the output levels. By replacing the regulator tubes with different stable voltages, it's easy to adjust the output range. In non-sinusoidal wave circuits, the oscillation frequency is independent of the Zener diode's stable voltage, so adjusting the amplitude does not affect the frequency. For triangular waves, amplitude can also be controlled by adjusting the upper and lower threshold voltages of the comparator. The amplitude is usually measured using an oscilloscope.
2. Waveform Adjustment: (1) Square waves are observed on an oscilloscope, focusing on the steepness of the rising and falling edges. If the edges are not sharp, it may indicate that the operational amplifier’s conversion rate is too low. A higher conversion rate should be used, especially at higher oscillation frequencies. (2) For triangular or sawtooth waves, the linearity of the rising and falling slopes is important. If the waveforms appear rounded at the peaks or valleys, it suggests poor linearity, which is often linked to the sharpness of the square wave edges. The steeper the square wave edges, the better the linearity of the triangular wave.
3. Frequency Adjustment: (1) Unlike sinusoidal circuits, non-sinusoidal circuits do not have a frequency selection circuit. Instead, the oscillation period depends on the energy change speed of the energy storage element in the integrator. This allows frequency adjustment through resistors, capacitors, or by changing the charging and discharging current of the current source. Adjusting the frequency via the integration circuit or capacitor does not affect the amplitude. (2) Frequency stability can be evaluated by measuring the relative change in frequency over time. Ensuring consistent frequency output is crucial for reliable operation, especially in applications requiring precise timing or synchronization.
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