A diode is a circuit component that only enables current to flow in one direction. Diodes come in different sizes, and they typically have a black cylindrical body with two leads coming to the sides (Anode and Cathode) and a stripe at the Cathode end. Diodes are like one-way streets. The current can only move from the Cathode end to the Anode end through the diode. This occurs because the diode prevents current from flowing in the opposite direction from the Anode side. A diode is reverse biased when it acts as an insulator and forward biased when it allows current flow. A diode’s anode and cathode are its two terminals. Diodes are used in circuits to limit voltage and convert AC to DC. Semiconductors like silicon and germanium are employed to get the most out of diodes. Even though they both transfer power in the same direction, the way they do so is different. Diodes come in various shapes and sizes, each with its own set of applications, such as Zener diodes. Switches, signal modulators, signal mixers, rectifiers, signal limiters, voltage regulators, etc., are all examples of diode applications.
Zener diodes are one of the diodes used for particular purposes. Except for one key distinction, Zener diodes work just like conventional diodes. The reverse-breakdown voltage of Zener diodes is known as “Zener Voltage.” This means that Zener diodes can only stop current from flowing through a circuit up to a particular voltage. If the reverse-breakdown voltage of a Zener diode is 10 V and the current flow is only 5 V, the Zener diode will block the current flow. In another scenario, if the circuit’s current flow is 11 V, the Zener diode will allow the current to pass.
What is the point of a diode that conducts in both directions? you might wonder. A Zener diode comes in handy when creating voltage regulators, over-voltage protection circuits, and other circuits. It may be used to navigate partial current flow in a different direction in a circuit. The construction of Zener diodes also differs from the construction of regular diodes. These diodes are manufactured from severely doped N and P-type semiconductors, varying amounts of doping to achieve varying breakdown voltages. As a result, different voltage levels of Zener diodes have varied voltage capacities.
In summary, Zener diodes are designed to be used in reverse-bias mode, with a low, steady breakdown voltage, or Zener voltage. They begin to conduct significant reverse currents. A Zener diode can work as a voltage regulator by functioning as an auxiliary load, pulling more current from the source when the voltage is too high and less current when the voltage is too low.
Clarence Melvin Zener was the one who initially described the benefits of this diode. Clarence Zener was a professor in the Department of Physics at Carnegie Mellon University. His research interests were in solid-state physics. He graduated from Stanford University in 1926 and obtained his doctorate from the same institution in 1929. In 1950, he invented the Zener Diode, which is now used in modern computer circuits. In 1934, Clarence Zener released a paper on the breakdown of an electrical insulator. He was known worldwide for pioneering a field of science called “internal friction,” which was the focus of most of his research.
You may be experiencing unknown or mysterious failures in your projects when utilizing voltage-sensitive motors or other components in a circuit. Voltage-sensitive components can sometimes burn because simply they cannot handle the amount of voltage in the current. Let’s take a look at the circuit figures. Circuit 1 has a 12 Volt power supply with a reverse-biased Zener Diode. The Zener voltage is 10 Volt; therefore, the breakdown voltage has been exceeded by the 12 Volt power supply and doesn’t allow more than 10 Volts to the Voltmeter. If we increase the voltage of the power supply to 90 Volts as shown in the circuit 2 diagrams, then the Zener Diode will still allow the current to flow past it. However, the current that goes to the Voltmeter is still about 10 volts. Hence, the Zener diode can be used to create a voltage regulator using this logic in a circuit.
Nominal voltage, power dissipation, forward drive current, forward voltage, packaging type, and maximum reverse current are attributes that are used to classify different Zener diodes. Let’s get to know some of these attributes.
Zener Breakdown Voltage is also called the Nominal Operation Voltage. It is one of the important parameters for Zener Diode selection.
The greatest amount of power that the Zener current can discharge is represented by this value. Exceeding this power rating causes the Zener diode to overheat, potentially damaging it and causing the failure of the components connected to it in a circuit. As a result, while choosing a diode for a specific application, this element should be considered.
Maximum Zener Current
At the Zener voltage, this is the maximum current that may be passed through the Zener diode without destroying it.
Minimum Zener Current
This is the minimum current required for the Zener diode to enter the breakdown area and begin working.
Other parameters that act as diode specifications must all be carefully studied before deciding on the type of Zener diode required for any particular design.
Microelectronics is a subfield of electronics that studies tiny complex machines or micro-chips that allow most of our devices to function, such as our cellphones. A microprocessor is a microchip. It is crucial in the field of microelectronics with billions of transistors per square centimeter, amplifying, controlling, and generating electrical signals. These transistors function as on and off switches that allow microelectronics to perform various Boolean operations by storing 1s and 0s. The Boolean operation or switching takes as little as 10 trillionths of a second. These transistors are tiny and unbelievably fast, allowing our modern devices to become smaller and faster in various applications.
Microelectronics has revolutionized the field of electronics and is rapidly transforming our lives and our world. The most fundamental building block of microelectronics, the transistor, was invented in 1947. John Bardeen Walter Brattain and William Shockley demonstrated the point-contact transistor to their co-workers at Bell Labs in New Jersey. The point-contact transistor is the first form of the transistor and was made from gold foil strips pressed into contact with a slab of Germanium on a plastic triangle. It is the size of a thumb which is much larger than the modern microscopic transistors.
Bardeen, Brattain, and Shockley connected a microphone to one end of the unit and a loudspeaker on the other to test the amplification. The men took turns picking up the microphone and whispering, “Hello.” “HELLO!” yelled the loudspeaker on the other end of the line. This moment is significant to microelectronics because it is followed by a technological revolution throughout the world. The progress in microelectronics has been focused on shrinking the circuitry embedded onto chips.
A decade later, Jack Kilby invented the integrated circuit (IC), a small circuit containing electronic components, including transistors, resistors, capacitors, and other components. Kilby worked for Texas Instruments, a semiconductor manufacturer, as an electrical engineer. Since each component had to be wired to any other component, he was irritated by the limited technical advancements. Because of the wires, the number of components used in devices was limited and sensitive to damage. Kilby constructed a circuit entirely out of semiconductors using Texas Instrument’s knowledge of silicon transistors and semiconductors. Kilby’s final product, the integrated circuit, eliminated the need to wire each part individually. It was much smaller than any other previously devised circuit.
In 1965 Gordon Moore, one of the co-founders of Intel, published his observation regarding the future of microelectronics in the Electronics Magazine. Moore stated that the computing power of integrated circuits would increase exponentially along with the advancement of transistors over time, while the cost would decrease exponentially. The size of transistors shrank dramatically, and the number of transistors used in circuits grew rapidly. Moore’s observation drew a lot of attention and became known in the scientific world as Moore’s law. Moore’s law continues to be an accurate prediction of microelectronics’ future.
Intel developed and introduced their first microprocessor, the 4004, chip in 1971. Intel designed the 4004 microprocessors with 2,300 transistors, which resulted in as much processing power as the room-filling ENIAC. Intel continually develops microprocessors with better processing powers that power most desktop computers to this day. The advancement of technology is at its peak, from phones to drones. Microelectronics plays a prominent role in humanity’s past and continuing progress in technology. Nanotechnology is expected to be the future of microelectronics, with far smaller components processing at much faster speeds.
Semiconductor memories are information-storage microelectronic circuits. There are two types of memories: read/write and read-only memories (ROMs). Silicon and Germanium are metalloids, and their crystalline structure enables them to conduct electricity while still acting as insulators, thanks to their chemical elements. In addition, silicon is the most abundant element in the Earth’s crust. These materials and other passive components such as resistors, inductors, and capacitors are used to create microelectronic devices. A silicon chip will serve as the base to activate and deactivate the components in a controlled manner to send signals for a brief period. Despite its great usefulness, however, silicon cannot satisfy all demands of microelectronics. Microelectronics manufacturers are in search of a faster and more invincible material to integrate into circuits.
Making any microelectronic system entails several measures. In this regard, integrated circuits are the most complicated. Circuit design and chip fabrication are the two parts of the process. When creating an integrated circuit, a complicated staging method is used to transmit a signal to the desired output 3. This necessitates reading a textbook, but an application on how the chip functions can be addressed.
RFID stands for Radio Frequency Identification. It is a wireless technology that uses a chip electromagnetic frequency to identify something. RFID systems are used in most passports, vehicles, contactless card payments, smartphones, key fob, and more. An RFID system consists of a transponder (tag) and a reader.
RFID readers are made up of a radio frequency module, a control unit, and an antenna that generated an electromagnetic field. On the other hand, a tag consists of a single antenna for receiving and transmitting signals and an integrated circuit (IC) that stores and processes data while controlling and decoding radio-frequency (RF) signals from the antenna.
An interaction happens between a tag and a reader when they are close enough to share an electromagnetic field. This interaction ignites voltage in the tag’s antenna to power up the tag’s microchip. The microchip receives power and data of requests from the reader and returns the requested data to the reader.
Since World War II, RFID technology has been a longstanding technology used to identify approaching friendly aircraft and enemy aircraft by the British military. The manufacturing of RFID chips has expanded in the last two decades. RFID technology has also enabled state-of-the-art techniques and advances in microelectronics health monitoring through contactless testing. Their use spread very quickly among many industries, from healthcare to ware stores.
To pursue a career as an Electronics Design Engineer, one must enroll in an ABET-accredited institution and pursue a bachelor’s degree in Electrical/Computer Engineering. Telecommunications engineering, signal processing, instrumentation, control engineering, and microelectronics are all subfields of an Electronic Design Engineer. An aspiring engineer must hone their expertise in product analysis, testing, and design to work in various industries. Working with project managers often requires coordination and time management in presenting, budgeting, completing tasks on time, and maintaining consistency. Nowadays, there are more specialized bachelor’s programs such as Microelectronic Engineering, where students can incorporate microelectronics or nanoelectronics circuits and sensors into a variety of products with a microelectronic engineering degree.
By: Arda Sengun & Richard Rojas
A voltage regulator is an electrical device whose sole purpose is to maintain a constant output voltage. It provides the desired output voltage regardless of any change in the input voltage or load conditions. Electronic circuits are dependent on voltage regulators since they require a stable voltage supply to avoid damage.
The voltage regulator uses the principle of a feedback control system. It relies upon negative feedback control loops.
As you can see, a reference voltage signal is provided to the comparator circuit along with the feedback signal from the controller. The comparator circuit compares both values and sends the error signal to the controller. The controller regulates the output voltage using the error signal from the comparator.
Throughout the world, voltage regulators are the most common electrical component in any machine or device. There are two fundamental types of voltage regulators:
A linear voltage regulator works like a voltage divider. The resistance of the linear regulator varies with the connected load and input voltage. Therefore, it is able to supply a constant voltage signal.
Linear regulators have a lot of advantages, for example, they provide a low ripple voltage which means less fluctuation in the output voltage signal. It has a fast response time. Moreover, it has low electromagnetic interference and less noise.
The efficiency of the linear voltage regulator is low and it dissipates a lot of heat so a heat sink is needed. It also requires more space. One of the main disadvantages is that the output voltage cannot exceed the input voltage.
A shunt regulator is used for low-powered circuits. It works by directing the current away from the load and sending it into the ground. It provides a path from the input voltage to a variable resistor which is connected to the ground. It has a very low efficiency but since the wasted current has a very low value, it is neglected.
The operation of a series voltage regulator is dependent upon the variable component which is connected with the load. When the resistance of the variable component is changed, the voltage drop across the component also changes. Using this technique, the voltage across the load remains the same.
One of the main advantages is that since the variable component and the load are connected in series, the current flowing through them is the same. Thus, the load effectively uses the current. Which makes it more efficient than a shunt regulator.
Switching voltage regulators consist of a series device that is repeatedly switched on and off at a high frequency. The duty cycle is used to control the amount of charge supplied to the load. The duty cycle is controlled by a feedback system that is very similar to the one in the linear regulator. Switching regulators have a high efficiency because the load is either on or off which means it dissipates no energy when it is off.
The switching regulator is superior to the linear regulator when it comes to the output voltage. Because it can supply an output voltage signal which can be greater than the input voltage. Furthermore, it can even generate an opposite polarity voltage signal.
Also known as a boost regulator, Step up regulators generate a higher output voltage signal by increasing the input voltage signal. This type of regulator is most commonly used to power multiple LEDs.
Step Down regulators are also called buck regulators. They supply a lower regulated output voltage signal from a higher unregulated input voltage signal.
The purpose of this regulator is to increase, decrease or invert the voltage signal. Moreover, it is also called a voltage inverter circuit. Opposite polarity is achieved by the forward and reverse biasing action of the diode. During the off-time, the circuit charges the capacitor and when the capacitor is fully charged, it supplies the opposite polarity output. The efficiency of this type of voltage regulator is very high.
Zener diodes have a mode due to which it can act as a voltage regulator. This mode is known as the reverse breakdown voltage operation. During this mode, the Zener diode maintains constant output DC voltage signal while the AC ripple voltage signal is completely blocked.
There are many applications of voltage regulators. One of the most common examples is the mobile charger. The adapter is supplied with an AC signal. However, the output voltage signal is a regulated DC signal.
Every power supply in the world uses a voltage regulator to provide the desired output voltage. Computers, televisions, laptops and all sorts of devices are powered using this concept.
Small electronic circuits rely on regulators to operate. Even the slightest fluctuation in voltage signal can damage the components of a circuit such as ICs.
When it comes to power generation systems, voltage regulators play an essential part in its operation. A solar power plant generates electricity based on the intensity of sunlight. It needs a regulator to ensure a regulated constant output signal.
Rheostats are resistors which are adjustable, and are used when applications require current adjustment or different resistance in an electrical circuit. Rheostats can adjust generator features, low lights, and start or stable the speed of electrical motors.
There are two things that affect the amount of current flowing into an electric circuit: the magnitude of the applied voltage and the overall resistance of that circuit. If the circuit resistance is lowered, the electric current flow that is passing through the circuit increases. Conversely, the electric current is limited if the circuit resistance is increased.
There is direct relation between the length of the wire to the resistance of the circuit. Increasing the length of the wire increases the resistance between in the circuit. Rheostats allows resistance to be changed, which in turn, either increases or decreases the current through the circuit. The need to add different resistors for varying resistances automatically disappears since a single rheostat can incorporate different resistances necessary for the circuit depending upon its range.
A rheostat is a wire wound variable resistor which has two connection points: one is a moving point and the other one is a fixed point. Similar to a potentiometer, some rheostats can have three connection points (A, B, and C) as shown in Figure 1, but still, only two of them are used. In such cases, there are two fixed points (A and C), only one of which is used, and the second connection point is the moving one (B).
Rheostats also have to bear large currents when compared with potentiometers. Therefore, rheostats are made up of wire wound resistors. They are mainly constructed by wrapping the Nichrome wire across a ceramic core. Such a core behaves as an insulator to the heat energy and does not permit it to flow through the rheostat.
Figure 1 explains the working principles of a rheostat. As mentioned above, rheostats work on the principle that the resistance of a certain track or wire depends upon its length. Let’s assume that we are using the fixed connection point A and the moving connection point B of the rheostat illustrated in Figure 1. The rheostat will offer minimum resistance to the circuit if the slider lies closer to point A, since the resistive coil length is at a minimum. Therefore, a large current can flow through the circuit in this case.
Similarly, the rheostat will offer maximum resistance if the slider lies closer to point C, as the resistive coil length is at its maximum. Hence, a tiny amount of current would flow through the circuit and a large part of the current would be opposed by the rheostat.
Now, let’s say that we are using the fixed connection point C and the moving connection point B. In this case, when the slider is made to lie near point C, the rheostat would offer minimum resistance and maximum current flow through the circuit. Likewise, when the slider is moved near to point A, the rheostat would offer maximum resistance and minimum current flow through the circuit.
Finally, it is important to know the maximum and minimum resistances necessary for your circuit. Rheostats have maximum and minimum resistance ratings, and thus, they cannot offer resistance outside their inherited range.
Now you may be wondering if there is a high point up to which the resistance may be decreased or elevated inside the rheostat. For all rheostats, they come with a resistance rating, for instance if 50kω is the rating of the rheostat, the minimum resistance it will deliver is zero and the maximum will be near 50kω.
Rheostats are used in situations where high voltage is needed to transmit electricity. They either work as a variable resistor or as a potential divider. An example of rheostats working as a variable resistor is in dimmers. Fan dimmers and light dimmers frequently use rheostats to control the variation of speed and the intensity of light respectively.
Rheostats are used to change the intensity of light when the lights are dim. The flow of electric current decreases through the bulb. If rheostats resistance is increased the light brightness is lessened. Similarly, The flow of electric current increases through the bulb. If rheostats resistance is increased, the light brightness is increased.
When the rheostat amplifies its resistance, the electric current through the bulb is reduced and the light dims. This same process would slow a ceiling or portable wall fan. Radios are equipped with rheostats to manage volume. Motor speeds can also be controlled through rheostats. They can also be used to control temperature in an oven, a heater or an apartment.
Rheostats also work as potential dividers. Wheatstone bridge applies the same potential dividing principle. Different types of resistive sensors use the potential dividing technique, strain gauges, light dependent resistors and thermistors. Rheostats can be used to measure the resistance of a sensor through a microcontroller. Rheostats can accomplish high voltage readings as well as accurate logic level shifting.
Rheostats are still a primary and common component to control the discharging of current in an electrical circuit. However, solid state devices like triacs and silicon-controlled rectifiers (SCR) have taken the place of rheostats. Rheostats are less efficient than a triac and are less reliable because of presence of mechanical components.
They are mostly when circuits need to be tuned or calibrated. High voltage power lines also use rheostats as potential dividers. Low current and high voltage induce minimal losses in power transmission. This helps supply electricity to millions of homes around the globe.
In the electronics industry, one of the most popular applications of semiconductor diodes is to convert alternating current (AC) signal of any frequency, which is typically 60 or 50 Hz, to a direct current (DC) signal. This DC signal can be used for powering electronic devices, rather than batteries. The circuit which converts the AC into DC signal commonly consists of a particular arrangement of interlocked diodes and is known as a rectifier. In power supply circuits, two types of rectifier circuits are commonly used — half-wave and full-wave. Half-wave rectifiers only permit one-half of the cycle through, whereas full-wave rectifiers permit both the top half and bottom half of the cycle through, while converting the bottom half to the same polarity as the top. This difference between them is shown in Figure 1.
Between the two types, the full-wave rectifier is more efficient as it uses the full cycle of the incoming waveform. There are two types of full-wave rectifiers — the center-tapped full-wave rectifier, which requires a center-tapped transformer, and the bridge rectifier, which does not need a center-tapped transformer. The bridge rectifier will be discussed in this article as it is the most popular and usually comes in preassembled modules, making them easier to use.
Bridge Rectifiers use four diodes that are arranged cleverly to convert the AC supply voltage to a DC supply voltage. The output signal of such a circuit is always of the same polarity regardless of the polarities of the input AC signal. Figure 2 depicts the circuit of a bridge rectifier with diodes interlocked in a bridge configuration. The AC signal is applied at the input terminals a and b, and the output is observed across the load resistor R1.
Let’s see how this rectifier circuit responds to an AC signal with changing polarities at every cycle:
Nonetheless, this output voltage of single polarity is not pure DC voltage, as it is pulsating and not a straight line in nature. This problem is quickly solved by connecting a capacitor in parallel with the load resistor as shown in Figure 3. In this new design, the positive half cycle will charge the capacitor via the diodes D2 and D3. And, during the negative half cycle, the capacitor will stop charging and will begin to discharge itself through the load resistor.
This process is known as filtration, and the capacitor acts as a filter. The capacitor has improved the pulsating nature of the output voltage, and it will now only have ripples. This waveform shape is now much closer to a pure DC voltage waveform. The waveform can be further improved by using other types of filters such as an L-C filter and pie filter.
The bridge rectifier just discussed is a single-phase type, however, it can also be extended to a three-phase rectifier. These two types can be further classified into full controlled, half controlled, or uncontrolled bridge rectifiers. The circuit that we just discussed is uncontrolled since we cannot control the biasing of the diode, but if all the four diodes are replaced with a thyristor, its biasing can be controlled by controlling its firing angle via its gate signal. It results in a fully controlled bridge rectifier. In a half controlled bridge rectifier, half of the circuit contains diodes, and the other half has thyristors.