What is a tuned circuit?
A tuned circuit is a specific arrangement of components within an electrical circuit that naturally operates at a desired frequency. It can be compared to the vibrations produced by a musical instrument, where a specific note is generated when the instrument’s string naturally vibrates at a particular length and elasticity. Similarly, the components within a tuned circuit are configured to produce a specific frequency.
Examples of Tuned Circuits
Here are a few examples of tuned circuits in various applications:
Radio Antennas: Radio antennas are tuned by adjusting their length to match the desired frequency. This ensures efficient reception and transmission of radio signals.
Crystal Oscillators: Crystal oscillators are devices that naturally produce a fixed frequency based on the properties of a crystal. They are commonly used in electronic devices such as clocks and communication systems.
Microwaves: Microwaves are guided by adjusting the shape of the cavity in which they bounce. This tuning process helps focus the microwaves and optimize their functionality.
555 Oscillator: The 555 oscillator is a popular integrated circuit used to generate stable waveforms at various frequencies. It can be tuned using a voltage bucket (capacitor) that takes a fixed time to recharge, allowing for frequency adjustments.
Working of a Tuned Circuit
An electrical circuit is considered a tuned circuit when it comprises an inductance circuit (inductor) and a capacitance, forming a resonant or tank circuit. Tuned circuits are commonly used in filters, frequency mixers, tuners, and oscillators to generate or pick up signals at specific frequencies.
There are two basic types of tuned circuits: serial and parallel. When a tuned circuit operates at its resonant frequency, it has the ability to store electrical energy. The inductor and capacitor within the circuit store this energy. The inductor stores energy in its magnetic field, while the capacitor stores energy between its plates.
The functioning of a tuned circuit involves the following steps:
Charging the Capacitor: When a charged capacitor is connected through an inductor, the charges flow through the inductor, creating a magnetic field around it. This magnetic field reduces the voltage across the capacitor, causing the entire load to dissipate, and the voltage across the capacitor drops to zero.
Current Inhibition: Due to the inductance, the current does not stop abruptly but continues flowing, albeit at a reduced rate. As the magnetic field gradually reduces, the current charges the capacitor with a voltage of the opposite polarity.
Recharging the Capacitor: Once the magnetic field completely disappears, the current ceases, and the capacitor is recharged again in the opposite polarity. This cycle repeats, resulting in oscillatory behavior within the tuned circuit.
In tuned circuits, these oscillations occur rapidly, with energy flowing back and forth through the inductor and capacitor.
Overall, tuned circuits play a crucial role in achieving specific frequencies in electronic systems. By carefully selecting the components and their properties, engineers can design circuits that resonate at desired frequencies, enabling efficient signal generation, filtering, and transmission.