Analogue electronics

Some signals change in small ways.

They do not jump from one level to another. Instead, they move smoothly like a slide.

An electrical signal can change its strength. It can also change how fast it moves. This helps a tool show things like heat or sound.

Sometimes, tiny bits of noise get in the way. This noise can be a small disturbance. It makes the signal harder to use.

Even with noise, you can still hear some things. This is why these systems fail slowly. They do not just stop working all at once.

Many tools use these smooth signals to work. They help us learn about the world.

Analogue electronics use signals that change smoothly. These signals do not jump between levels. Instead, they can take any value in a range. This is called an analogue signal. The word analogue means proportional. This means the signal changes in step with the thing it measures.

A transducer is a part that changes one kind of power into another. For example, a microphone is a transducer. It turns sound into an electrical signal. If a sound gets louder, the signal gets bigger too. This is a direct link between the sound and the signal.

Sometimes, random noise gets into these systems. Noise is a small, unwanted disturbance. It can come from tiny vibrations in atoms. This noise can make a signal hard to use. However, analogue signals fail gracefully. This means they still work a little even with much noise.

Digital electronics are different. They use signals that jump between levels. A digital signal might look like the one in this picture.

Most digital tools still need analogue parts. They use an interface to talk to the real world. An ADC is a tool that turns analogue signals into digital numbers. A DAC does the opposite. It turns numbers back into an analogue signal.

Analogue electronics use signals that change smoothly. These signals do not jump between levels like digital ones do. The word analogue comes from a Greek word meaning proportional. This means the signal stays in step with what it measures. For example, a signal might represent temperature. If one volt means one degree, then 10 volts means 10 degrees. Every tiny change in the signal carries new information.

These systems work by using a transducer to move energy. A transducer is a tool that changes one type of energy into another. A microphone is a great example of this. It turns the pressure of sound into an electrical signal. If the sound gets louder, the electrical signal gets larger too. You can also use modulation to carry a signal. This involves changing properties like amplitude or frequency.

Designing these circuits can be a very hard job. Engineers often have to design them by hand. This is because the way the circuit works is built right into the hardware. In the 1970s, IBM helped make this easier. They created a tool called ASTAP to simulate circuits. Today, engineers use software simulators like SPICE to help them. These tools make it faster to test new ideas.

Analogue signals face a problem called noise. Noise is a random disturbance in the signal. It can come from the tiny vibrations of atoms. It can also come from other signals nearby. This noise can make a signal harder to read. However, analogue signals are said to fail gracefully. This means they can still work even with a lot of noise.

Most digital devices still need analogue parts to work. They use an ADC to turn analogue signals into binary numbers. This is called an analogue-to-digital converter. To play that signal back, they use a DAC. This is a digital-to-analogue converter. It turns the numbers back into a smooth signal. This allows digital tools to talk to our real world.

Analogue electronics are systems that use continuously variable signals to carry information. This is different from digital electronics, where signals usually jump between only two specific levels. The term analogue comes from a Greek word meaning proportional. In these systems, there is a direct, proportional relationship between a signal and the voltage or current used to represent it. Every tiny change in the signal represents a different level of the phenomenon being measured. This makes analogue systems very sensitive to the physical world around them.

To work, these systems often rely on a transducer. A transducer is a device that converts one type of energy into another. For example, a microphone acts as a transducer by turning sound pressure into electrical signals. When a sound strikes a microphone, the variation in pressure creates a corresponding change in current or voltage. If the volume of the sound increases, the electrical fluctuation increases proportionally. Other ways to convey signals include modulation. In amplitude modulation (AM), the amplitude of a waveform is altered by the source information. In frequency modulation (FM), the frequency is changed instead. Other methods include phase modulation, which alters the phase of the carrier signal.

Analogue signals can be categorized by the components used to build them. Some circuits are entirely passive, meaning they consist only of resistors, capacitors, and inductors. Other circuits are active because they contain active elements like transistors. There is also a difference in how components are arranged. Traditional circuits use lumped elements, which are discrete, separate components. In contrast, distributed-element circuits are built from pieces of a transmission line. These different types allow engineers to build everything from simple sensors to complex radio receivers.

One major challenge in analogue electronics is inherent noise. Noise consists of random disturbances or variations in a signal. Some noise is caused by the random thermal vibrations of atomic particles. Other noise can come from crosstalk between different signals or from poorly designed components. Because every change in an analogue signal is meaningful, any disturbance appears as noise. As a signal is copied or sent over long distances, these variations can cause signal degradation. To fight this, engineers use shielding and low-noise amplifiers (LNA) to reduce disturbances.

Analogue and digital systems handle noise in very different ways. Analogue signals are said to "fail gracefully." This means that even with very high levels of noise, the signal can still contain intelligible information. Digital signals do not show much effect from noise until a certain threshold is reached. Once that limit is hit, digital systems fail catastrophically. In digital systems, signals are regenerated at each logic gate to remove noise. In analogue systems, signal loss is managed with amplifiers, but the amplifier itself adds more noise to the system according to its noise figure.

Precision in analogue systems is limited by physical factors. Shot noise in components creates a fundamental limit on how much detail a signal can show. To bridge the gap between the physical world and computers, engineers use converters. An analogue-to-digital converter (ADC) takes an analogue signal and changes it into a series of binary numbers. This is used in digital sound recording and data acquisition. To turn that data back into something we can hear or see, a digital-to-analogue converter (DAC) is used. The DAC takes binary numbers and converts them back into a continuous analogue signal.

Designing analogue circuits is often more difficult than designing digital ones. Digital hardware is highly standardized and can be mass-produced using repeated identical blocks. Analogue circuits are usually designed by hand because the specific application is built directly into the hardware. However, technology has helped make this easier. In the 1970s, IBM developed a simulator called ASTAP that used a sparse matrix method for circuit analysis. Today, engineers use software circuit simulators like SPICE to prototype designs much faster. Even in a digital world, every device that interacts with the real world still requires an analogue interface.