1.2.2. Input and Output Signals

Whenever we say electronic circuit what we mean is that, if I look into the circuit as a black box. To make this circuit working, we need to put the power on and apply a signal at the input port, then observe the corresponding effect at the output.

An electronic circuit can be imagined as a black box where you need to provide power for it to function. Once the circuit is powered, you feed an input signal through an input port. The circuit then processes this input and produces an output signal, which you can measure. This process helps in understanding how electronic devices work by comparing what you send in with what comes out.

Think of an electronic circuit as a coffee machine. To make coffee (the output), you need to turn it on (power it up) and add coffee grounds and water (input). Once the machine processes those ingredients, you get a cup of coffee as the final output. Likewise, in electronic circuits, you input signals and receive outputs after processing.

In this context, we mainly focus on signals as either voltage or current. Non-electrical signals can be converted into electrical signals, which represent the input and output.

When we talk about signals within electronic circuits, we usually refer to them as voltage or current. In most cases, a non-electrical signal (like sound or light) is transformed into electrical signals for processing. Thus, we can analyze and manipulate different types of input signals in a way that electronic systems can understand, leading to output signals that can similarly be in voltage or current form.

Imagine a voice command to your smart speaker. Your voice is a sound signal (non-electrical). The speaker converts this sound into an electrical signal, processes it, and then produces an output, like playing a song or answering your question, which you can hear (current output).

We can classify signals into two main types: analog and digital. Analog signals have continuously variable values, while digital signals have discrete levels.

Signals can be categorized primarily into analog and digital signals. Analog signals exhibit continuous changes, meaning they can take any value within a range. For instance, the volume of music can be adjusted to various levels smoothly. In contrast, digital signals only take on defined or discrete values, such as those represented in binary form (0s and 1s), which can signify different levels, such as 'off' or 'on'.

Think of an analog signal like a dimmer switch for lights. You can adjust the brightness gradually to any level. On the other hand, a digital signal is like a light switch where you can only choose between 'on' (fully bright) or 'off' (completely dark) without in-between levels.

Signals can also be differentiated based on their time representation: continuous time signals are available at all times, while discrete time signals are only available at specific intervals.

In addition to analog and digital, signals can be further broken down into continuous and discrete time signals. Continuous time signals are present at every instant and can vary smoothly over time. Conversely, discrete time signals are only captured at certain predefined intervals, like snapshots taken of a moving object. This distinction is essential in signal processing and circuit design because it determines how signals are manipulated and stored in electronic systems.

Think of continuous signals like a flowing river where you observe the water continuously moving at every point. On the contrary, discrete signals are like photographs taken of that river at different times, capturing only specific moments in its flow.

Circuits can be classified based on the type of signals they work with: analog circuits respond to analog signals, digital circuits handle digital signals, and mixed signal circuits deal with both.

Circuits are broadly categorized into three types based on the signals they process. Analog circuits are designed to work with analog inputs and outputs, such as audio amplifiers. Digital circuits work only with digital signals, transforming them into various logic levels. Mixed signal circuits can handle both analog and digital signals, allowing for a combination of functionalities, which is crucial in modern electronic devices.

Consider a smartphone. Its analog circuits process sound for calls, while digital circuits manage your apps and interface. Meanwhile, the parts that handle both, such as an audio jack that processes digital music files and converts them into sound, represent mixed signal circuits.

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