The RC network's actual phase depends on the chosen resistor and capacitor value for the desired frequency. By cascading several RC networks, we can obtain degrees of phase shift at the chosen frequency. This cascade of networks forms the base for the RC oscillator, otherwise known as Phase Shift Oscillator.
Adding an amplifying stage utilizing a bipolar junction transistor or inverting amplifier, we can produce a degree phase shift between its input and output to provide the full degree shift back to 0 degrees that we require, as mentioned above. The primary RC Oscillator circuit produces a sine wave output signal using regenerative feedback obtained from the RC ladder network. Regenerative feedback occurs due to the ability of the capacitor to store an electric charge.
The Resistor Capacitor feedback network can be connected to produce leading phase shift phase advance network or can be connected to create a lagging phase shift phase retard network. One or more resistors or capacitors from the RC phase shift circuitry can be changed to modify the frequency of the network.
This change can be made by keeping resistors the same and using variable capacitors because capacitive reactance varies with frequency. However, for the new frequency, there could be a requirement to adjust the amplifier's voltage gain. If we choose the resistors and capacitors for RC networks, then the frequency of RC oscillations would be:. However, the combination of the RC Oscillator network works as an attenuator, and it reduces the signal by some amount as it passes through each RC stage.
So voltage gain of the amplifier stage should be sufficient to restore lost signal. The RC network needs to be connected to the inverting input of the Op-Amp, making it the inverting amplifier configuration.
The inverting configuration gives degrees of phase shift at the output, leading to a total of degrees combined with the RC networks. The other configuration of RC oscillator is the operational amplifier phase lag oscillator. LC or Inductor-Capacitor Oscillator is a type of oscillator which utilizes a tank circuit to produce positive feedback for sustaining oscillation.
The schematic contains an inductor, capacitor, and also an amplifying component. The tank circuit is a capacitor and inductor connected in parallel, the diagram above also includes the switch and voltage source for ease of demonstration of the working principle when the switch is connecting the capacitor to the voltage supply, the capacitor charges.
When the switch connects the capacitor and inductor , the capacitor discharges through the inductor. The increasing current through the inductor starts to store energy by inducing an electromagnetic field around the coil.
When the switch connects the capacitor and inductor, the capacitor discharges through the inductor. After discharging the capacitor, the energy from it has transferred into the inductor as an electromagnetic field. As the energy flow from the capacity decreases, current flow through the inductor decreases - this causes the inductor's electromagnetic field to fall as well.
This back EMF then begins to charge the capacitor. Once the capacitor has absorbed the energy from the inductor's magnetic field, the energy is stored once again as an electrostatic field within the capacitor. If we had an ideal inductor and capacitor, this circuit could generate the oscillations forever. However, a capacitor has current leakage, and inductors have resistance.
In real life, however, the oscillations would look as below, as energy is lost. This loss is called damping. If we want to sustain the oscillations, we need to compensate for the loss of energy from the tank circuit through the addition of active components to the circuit, such as bipolar junction transistors, field-effect transistors, or operational amplifiers. The primary function of the active components is to add the necessary gain, help generate positive feedback, and to compensate for the loss of energy.
The tuned collector oscillator is a transformer and a capacitor connected in parallel and switched with a transistor. This circuit is the most basic LC oscillator schematic. The primary coil of the transformer and capacitor forms the tank circuit, with the secondary coil providing positive feedback, which returns some of the energy produced by the tank circuit to the base of the transistor.
This circuit consists of two capacitors in series, forming a voltage divider , which provides feedback to the transistor, with an inductor in parallel. While this oscillator is relatively stable, it can be hard to tune and is often implemented with an emitter follower circuit so as not to load the resonant network.
To overcome the difficulties tuning the Colpitts oscillator to a specific frequency in production, a variable capacitor in series with the inductor is often added, forming a Clapp Oscillator. This modification allows the circuit to be tuned during production and servicing to the specific frequency required.
Unfortunately, this type of LC oscillator is still quite sensitive to temperature fluctuations and parasitic capacitances. Piezoelectric ceramic material with two or more metal electrodes typically 3 forms the basis of a ceramic resonator. In an electronic circuit, the piezoelectric element resonates mechanically, which generates an oscillating signal of a specific frequency - like a tuning fork.
Ceramic resonators are low cost; however, the frequency tolerance of ceramic resonators is only about - ppm. This tolerance of 0. With frequencies from below 1kHz to beyond 1GHz, there is a range of different materials and vibration modes that ceramic resonators use.
It can be essential to understand the method of resonance used in a device you are placing into your design. Environmental factors such as vibration and shock could impact the function of the resonator within your circuit. The Quartz oscillator is the most common type of crystal oscillator on the market. Where accuracy and stability are critical, the primary choice is crystal oscillators and their variants. A crystal oscillator stability is measured in ppm parts per million , and stability could be somewhere around 0.
An RC oscillator's stability can at best be 0. A quartz crystal can oscillate with very little power required to keep it activated compared to many other oscillators, making them perfect for low power applications. There are basically two oscillators, i.
Relaxation oscillators can be built using several different designs and can work at many different frequencies.
Astables may typically be chosen for such tasks as producing high frequency digital signals. They are also used to produce the relatively low frequency on-off signals for flashing lights. A sweep waveform is another name for a saw-tooth wave. This has a linearly changing e. Sweep oscillators often consist of a ramp generator that is basically a capacitor charged by a constant value of current. Keeping the charging current constant whilst the charging voltage increases, causes the capacitor to charge in a linear fashion rather than its normal exponential curve.
At a given point the capacitor is rapidly discharged to return the signal voltage to its original value. These two sections of a saw-tooth wave cycle are called the sweep and the fly-back. Hons All rights reserved. The signals used in the oscillators are a sine wave and the square wave. Some of the examples are the signals are broadcasted by the radio and television transmitter, clocks which are used in computers and in video games.
There are two types of oscillator circuits available they are linear and nonlinear oscillators. The linear oscillators give the sinusoidal input. The linear oscillators consist of a mass m and its force in the linear equilibrium. The different types of oscillator circuits are mentioned below and some of them are explained. The Armstrong oscillator is an LC electronic oscillator and to generate this oscillator we are using the inductor and the capacitor.
In the US engineer Edwin Armstrong has invented the Armstrong oscillator and it was the first oscillator circuit and also in , this oscillator was used in the first vacuum tube by Alexander Meissner who was an Austrian engineer. The Armstrong oscillator is known as the tickler oscillator because the individual features of the feedback signal should produce the oscillations that are magnetically coupled to the tank indicator.
Let us consider the coupling is weak, but the sustained oscillation is sufficient. The following equation shows the oscillation frequency f.
The Armstrong oscillator is also called the Meissner oscillator or tickler oscillator. To achieve the degree phase shift oscillation, the Armstrong oscillation uses the transistor, which is shown in the above figure.
From the figure, we can observe that the output is from the primary transformer it has a transistor and the feedback is taken from the secondary coil of the transformer. The sine wave that matches that particular frequency will get amplified by the resonator, and all of the other frequencies will be ignored. In a radio, either the capacitor or the inductor in the resonator is adjustable. When you turn the tuner knob on the radio, you are adjusting, for example, a variable capacitor.
Varying the capacitor changes the resonant frequency of the resonator and therefore changes the frequency of the sine wave that the resonator amplifies. This is how you "tune in" different stations on the radio! Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Solid State Electronics. How Oscillators Work.
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