A Guide to Oscillating Frequencies in Electronics

January 19, 2021 Cadence PCB Solutions

Key Takeaways

  • Learn what oscillating frequencies are.

  • Explore applications of oscillating frequencies in electronics.

  • Understand how to compensate for energy loss in oscillators. 

When I was actively playing the piano, I had an almost perfect sense of rhythm. Even without a metronome, I’ll have no problems keeping the beats throughout the entire piece of music. It has been a couple of decades since I last laid my fingers on a piano. My sense of rhythm has regrettably deteriorated.

These days, I keep missing the beats when humming to a favorite tune. It’s a perfect example of how the lack of practice could dull senses. And I have to swallow my pride by making the metronome my best friend again. The metronomes swinging pendulum rod reminds me of the role of oscillating frequencies in electronics. 

What Are Oscillating Frequencies?

Perhaps the best way to visualize oscillating frequencies is to think of ocean waves. The waves have their highs and lows as they hit the shore repetitively. As you pay attention to the waves, you’ll be hypnotized by the periodic crashing sound.

There are three important elements for oscillating frequencies: the time period, amplitude, and wavelength. The time period indicates the interval between a complete cycle of the oscillation, whereas the amplitude is the maximum and minimum points of the oscillation. 

A graphic showing how amplitude, period, and time contribute to oscillation in waveform

How oscillation looks like in a waveform.

From the time period, the frequency of the oscillating wave can be calculated by the following formula:

Frequency (f) = 1/ Time period

Whether it’s oceanic waves or sound, it takes a minimum physical distance to complete a single cycle of oscillation. This parameter is termed wavelength and it’s a physical measurement between the same point on consecutive intervals. 

Oscillating Frequencies in Electronics

In electronics design, you’re bound to stumble on oscillating frequencies and their respective circuits. Many components depend on precise oscillating frequencies to function. Unlike the natural oceanic waves, oscillating waveforms in electronics are often not uniform in time period and amplitude.

A steady and precise oscillating frequency is used for powering real-time clocks in designs. The clock depends on a crystal, often a 32.768 Khz one, to provide the required “ticks” for incrementing the clock registers. Microcontrollers also depend on the uniform oscillating frequency to execute its code at the required speed.

Oscillator circuits are also found in TV, radio, and other types of RF transmitters. They generate the carrier signal with a particular frequency, which is then modulated by the information. On the receiving side, a resonator is tuned to the oscillating frequency to pick up and demodulate the RF signal. 

There are a few types of oscillators but at the core of them would be the LC circuit. It is also known as an LC tank circuit. The current oscillates between a fully charged capacitor and an inductor based on the Lenz law. When the inductor is charged, a back-emf that opposes the changes the current is generated, which charges the capacitor in the opposite direction. 

LC tank circuit

LC tank circuit, a common core of oscillator circuits.

Energy Losses in Oscillating Frequencies

Ideally, an LC circuit will produce a continuous oscillating waveform with equal amplitude once the cycle is initiated. However, a perfect sinusoidal oscillating waveform isn’t possible in a real-world LC circuit. The impedance of the components and connections result in energy losses over time.

Damped oscillation

Damped oscillation with gradually decreasing amplitude.

As a result, you’ll have a damped oscillation, where the amplitude gradually decreases. For an LC circuit to achieve continuous oscillation, it needs to be fed with a feedback signal. The feedback signal is used to amplify the existing one and to compensate for the loss. 

Practical application of an oscillator circuit often involves variants like tuned-collector oscillator, tuned-based oscillator, Hartley oscillator, and Colpitts oscillator. These oscillator circuits use either a transistor or an op-amp to amplify the oscillating signal. 

When designing a self-sustainable oscillating circuit, it is important to ensure that it is neither overdamped or underdamped. This means ensuring that the closed-loop gain, Aβ equals 1. A is the gain of the amplifier circuit while β equals the feedback network gain. 

The calculation for the closed-loop gain is more complicated than determining the oscillating frequency. Hence, using the right PCB design software helps in cutting short design time. Allegro PCB Editor will allow for a more efficient design process, while Allegro PSPICE designer provides useful simulation capabilities.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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