1.2. Electronic Circuits

Whenever we say electronic circuit what we are looking for it is that, if I look into the circuit as a black box. So, if I say that this is my electronic circuit, to make this circuit working what I need to do it is we need to put the power on. So, we can give a DC supply to activate the circuit. So, we are having this electronic circuit here and then once it is getting energized then you can apply the signal at the input port. And then you can consider the corresponding effect at the output, namely you would like to see what will be the corresponding output coming to this circuit.

In an electronic circuit, we treat the circuit as a 'black box' where we focus on the input and output rather than the internal workings. To operate this circuit, we first need to supply it with power, typically through a direct current (DC) source. Once the circuit is powered, we can input a signal, which the circuit will process, and we can then observe the output signal. The output signal is affected by the input signal and the design of the circuit itself.

Think of an electronic circuit like a coffee maker. You plug it in (power it on) and put in coffee grounds and water (input signal). Once you press the start button, the coffee maker brews coffee and pours it into a carafe (output signal). The way the coffee tastes depends on how you set it up, just as the output of an electronic circuit depends on how it is designed.

So, whenever we say that electronic circuit, whenever we are talking about electronic circuit; it is basically it consists of different electronic devices. So, within this one we do have electronic devices and those devices are getting activated by this DC and they should be in proper region of operation and so on. So, those details we will be seeing later, but whenever you are talking about see signal, what we mean by signal? In this case as an example, we are saying the signal can be voltage.

An electronic circuit is made up of various electronic devices such as resistors, capacitors, transistors, and others. These devices must be properly powered and operational to function correctly. When we refer to 'signals' in this context, we primarily mean electrical signals, which can be in the form of voltage. These signals can be input (the signals we provide to the circuit) or output (the signals we receive from the circuit). Inputs and outputs can be in the form of either voltage or current.

Consider a simple light bulb connected to a battery. The battery acts as the power source. When you connect the circuit (power on), the electrical signal (current) causes the bulb to light up (output signal). Here, the voltage is the signal that enables the bulbs to function.

Whenever we say a types of signals, it is we are assuming signal means it is voltage changing with time. So, the x-axis is t and then y-axis it is voltage, for the time being let you consider it is V and then this is time axis t, it may be seconds, milliseconds, microseconds and so and so, so this is in the scale of voltage. And then, it may be changing with respect to time like this.

Signals can be classified into various types based on how they change with time. An analog signal is one that varies continuously, represented as a smooth curve on a graph where voltage changes over time. In contrast, digital signals consist of discrete levels, typically shown as square waves or stepped lines in a graph, where the voltage remains constant until it jumps to another level. The distinction between these types of signals is critical in electronic circuits as it determines how information is processed.

Imagine a dimmer switch for a light. When you slowly turn the knob, the light smoothly transitions from off to fully bright, which represents an analog signal. On the other hand, a traditional switch just turns the light on or off with no dimming in between; this represents a digital signal.

Depending on the emphasis and the allowable levels of the signal, the signal can be different types; namely analog and digital kind of signal. In contrast to that, in case if we are having a special situation where the signal, it is having distinct levels; may be here also we may say that say V(t), but it may be having say two distinct levels, may be either high or low and so and so. In between if there is any transition we may ignore, we may ignore this transition levels and the acceptable or meaningful levels are only say this one or say whatever the level we do have.

Signals can be generally categorized as analog or digital based on their characteristics. Analog signals can take on any value within a range, making them continuous. Digital signals, however, have distinct levels (like 'high' and 'low') without any values in between, which is why they are often represented in binary (1s and 0s). This differentiation is vital in electronic systems, as it impacts how data is transmitted and processed.

Using a water faucet as an analogy, when you turn the handle very gently (analog), the water flow can gradually increase from a drip to a steady stream. But if you turn it on or off quickly (digital), you only get either a steady stream or no water at all. The gradual changes in water flow represent analog; the abrupt changes represent digital.

So, we may have a scenario where we may have one circuit here, another circuit here and so and so. Now each of these circuits, they may have their own functionalities to perform. And let me assume that the signal it is propagating from left hand towards the right.

In modern electronic systems, circuits can combine both analog and digital components, known as mixed signal systems. This means the system can process and handle signals that are both continuous (analog) and discrete (digital). The ability to interface these two types of signals allows for more complex functionalities and improved communication with the real world.

Think of a smartphone. When you make a phone call (analog signal) while being able to send a text message (digital signal), the smartphone is designed as a mixed signal device. It can handle both voice communication and data communication simultaneously.

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