- A mechanical or electronic device known as an oscillator operates on the oscillation principle, which describes a periodic fluctuation between two objects based on energy changes. Metal detectors, clocks, watches, radios, and computers are just a few examples of the numerous gadgets that use oscillators.
- Essentially, an oscillator is a signal generator that generates a sinusoidal or non-sinusoidal signal at a specific frequency. Oscillators have a wide range of uses because they are an essential part of all electrical and electronic circuits.
- An oscillator’s operation is based on continuous oscillations. An oscillator is sometimes described as an amplifier with positive feedback. Alternatively, a feedback amplifier with an open loop gain of one or slightly higher.
- Oscillators are referred to as generators at the time of definition. However, oscillators are more precisely energy converters that change dc energy into corresponding ac energy. The ac signal’s frequency ranges at the oscillator’s output oscillate between a few Hz and several GHz.
- We already know that an amplifier requires an ac input signal, which is amplified and obtained at the amplifier’s output. However, an oscillator just needs dc voltage to generate an ac signal with the desired frequency.
The oscillator is mainly classified based on the signal generated at its Output
Sinusoidal or Harmonic Oscillator
- Here, the oscillator’s obtained signal exhibits continuous sinusoidal variation as a function of time.
Non-sinusoidal or Relaxation Oscillator
- In this instance, the obtained signal at the oscillator’s output exhibits a sharp rise and fall at various voltage levels. resulting in the creation of waveforms like a square wave, sawtooth wave, etc.
Working of Oscillator
- A circuit known as an oscillator generates an uninterrupted, repetitive, and alternating waveform without any input. Fundamentally, oscillators change the unidirectional current flow from a DC source into an alternating waveform with the desired frequency, as determined by the elements in its circuit.
- By examining the behavior of an LC tank circuit, such as the one seen in Figure 1 below, which consists of an inductor L and a capacitor C that has been fully charged, it is possible to comprehend the fundamental concept underlying oscillators’ operation. The capacitor here initially begins to discharge through the inductor, converting its electrical energy into an electromagnetic field that may be stored in the inductor. There won’t be any current flowing through the circuit until the capacitor has fully discharged.
- However, at that time, the electromagnetic field would have been stored, creating a back-emf that causes the circuit’s current to flow in the same direction as previously. The electromagnetic field remains in place until it collapses, at which point electromagnetic energy is converted back into electrical form, starting the cycle all over again. But now since the capacitor would have been charged with the opposite polarity, the output would have been an oscillating waveform.
- The oscillations that result from the interconversion of the two energy forms, nevertheless, cannot last indefinitely since they will experience energy loss as a result of the circuit’s resistance. As a result, these oscillations’ amplitude gradually drops to become zero, making them naturally moist
- This suggests that one must account for energy loss to get oscillations that are continuous and have a constant amplitude. However, it should be noted that to achieve oscillations with constant amplitude, the energy provided must be properly managed and must be equivalent to the energy lost.
- This is because if the energy supplied is greater than the energy lost, the oscillations’ amplitude will rise (Figure 2a), producing a distorted output, whereas if the energy supplied is lower than the energy lost, the oscillations’ amplitude will fall (Figure 2b), producing uncontrollable oscillations.
- Practically speaking, oscillators are nothing more than amplifier circuits with positive or regenerative feedback, which allows for the feeding of a portion of the output signal to the input (Figure 3). The back-fed in-phase signal is held accountable for maintaining the oscillations by compensating for circuit losses in this amplifier, which is made up of an amplifying active element that can be a transistor or an Op-Amp.
- Because of the electronic noise in the system, oscillations start as soon as the power source is turned ON. This noise signal circulates inside the loop, is amplified, and quickly condenses to a single frequency sine wave. The oscillator depicted in Figure 3’s closed-loop gain expression is as follows
- Where A is the amplifier’s voltage gain and is the feedback network’s gain. Here, the oscillations will get more pronounced if A > 1 (Figure 2a), while they will become more muted if A 1. (Figure 2b). On the other hand, oscillations with constant amplitude result when A = 1 (Figure 2c). To put it another way, this shows that if the feedback loop gain is small, the oscillation dies out, whereas if the feedback loop gain is large, the output will be distorted. Only if the feedback loop gain is unity, however, will the oscillations be of constant amplitude, resulting in a self-sustained oscillatory circuit.
Application Of Oscillator
- Quartz watches (which use a crystal oscillator).
- Used in various audio systems and video systems.
- Used in various radio, TV, and other communication devices.
- Used in computers, metal detectors, stun guns, inverters, ultrasonic and radio frequency applications.
- Used to generate clock pulses for microprocessors and micro-controllers.
- Used in alarms and buzzes.
- Used in metal detectors, stun guns, inverters, and ultrasonic.
- Used to operate decorative lights (e.g. dancing lights).