Kingtronics Blog

The valve arrester consists of disks of zinc oxide material that exhibit low resistance at high voltage and high resistance at low voltage. By selecting an appropriate configuration of disk material, the arrester will conduct a low current of a few milliamperes at normal system voltage. During conditions of lightning or switching surge over voltage, the surge current is limited by the circuit; and for the magnitudes of current that can be delivered to the arrester location, the resulting voltage will be limited to controlled values, and to safe levels as well, when insulation levels of equipment are coordinated with the surge arrester protective characteristics.

A typical surge arrester consists of disks of zinc oxide material sized in cross-sectional area to provide desired energy discharge capability, and in axial length proportional to the voltage capability. The disks are then placed in porcelain enclosures to provide physical support and heat removal, and sealed for isolation from contamination in the electrical environment.

To analyse the electrical response of a quartz crystal resonator, it is very often useful to depict it as the equivalent electrical components that would be needed to replace it. This equivalent circuit is can then be used to analyse its response and predict its performance. The basic equivalent circuit of a crystal is shown below. In this circuit C1 represents the capacitance between the electrodes. L, C, and R represent the vibrational characteristics of the crystal. The inductance results from the mass of the material, C from the compliance, and R arises from the losses of which the greatest contributor is frictional losses.

Looking at this circuit it can be seen that there are two ways in which the circuit can resonate. One is from the resonance of L and C which provides a series resonance, giving a very low value of impedance at resonance. This is determined by the value of the resistance R. In this mode the external circuit has very little effect on the crystal resonance.

Schottky Rectifiers have been used in the power supply industry for approximately 15 years. During this time, significant fiction as well as fact has been associated with this type of rectifier. The primary assets of Schottky devices are switching speeds approaching zero-time and very low forward voltage drop (VF). This combination makes Schottky barrier rectifiers ideal for the output stages of switching power supplies. On the negative side, Schottky devices are also known for limited high-temperature operation, high eakage and limited voltage range BVR. Though these limitations exist, they are quantifiable and controllable, allowing wide application of these devices in switch mode power supplies.

Zener diodes regulate voltage by acting as complementary loads, drawing more or less current as necessary to ensure a constant voltage drop across the load. This is analogous to regulating the speed of an automobile by braking rather than by varying the throttle position: not only is it wasteful, but the brakes must be built to handle all the engine's power when the driving conditions don't demand it. Despite this fundamental inefficiency of design, zener diode regulator circuits are widely employed due to their sheer simplicity. In high-power applications where the inefficiencies would be unacceptable, other voltage-regulating techniques are applied. But even then, small zener-based circuits are often used to provide a “reference” voltage to drive a more efficient amplifier circuit controlling the main power.

Tantalum Capacitors are inherently polar devices and may be permanently damaged or destroyed if connected with the wrong polarity. The positive terminal is identified on the capacitor body by a polarity mark and the capacitor body may include an obvious geometrical shape.

However, some Series contain two capacitors connected (negative-to-negative) to form “non-polar” capacitors. Rated voltage  may be applied to these Series in either direction.

Sometimes the product cost may also impact the chosen footprint. For example, if a 1210, 22uF capacitor is more than double the cost of a 1206, then the 1206 component may be preferred. In other applications, the designer may just want to get the maximum capacitance in a limited available footprint. If, for example, there is only room for a 1206 capacitor, the 47uF part will still have the most capacitance even if it loses a larger percentage of its value than the 22uF or the 10uF parts.

The low leakage and high capacity of tantalum capacitors favors their use in sample and hold circuits to achieve long hold duration, and some long duration timing circuits where precise timing is not critical. They are also often used for power supply rail decoupling in parallel with film or ceramic capacitors with low ESR and reactance at high frequency. Tantalum capacitors can replace aluminum electrolytic capacitors in situations where the external environment or dense component packing results in a sustained hot internal environment and where high reliability is important. Equipment such as medical electronics and space equipment that require high quality and reliability make use of tantalum capacitors.

Low-voltage tantalum capacitors are commonly used in large numbers for power supply filtering on computer motherboards and in peripherals due to their small size and long-term reliability.

One of the most common uses for modern low-power potentiometers is as audio control devices. Both linear potentiometers and rotary potentiometers are regularly used to adjust loudness, frequency attenuation and other characteristics of audio signals. The 'log pot' is used as the volume control in audio amplifiers, where it is also called an "audio taper pot", because the amplitude response of the human ear is also logarithmic. It ensures that, on a volume control marked 0 to 10, for example, a setting of 5 sounds half as loud as a setting of 10. There is also an anti-log pot or reverse audio taper which is simply the reverse of a logarithmic potentiometer. It is almost always used in a ganged configuration with a logarithmic potentiometer, for instance, in an audio balance control.

For most power application, half-wave rectification is insufficient for the task. The harmonic content of the rectifier’s output waveform is very large and consequently difficult to filter. Furthermore, the AC power source only supplies power to the load one half every full cycle, meaning that half of its capacity is unused. Half-wave rectification is, however, a very simple way to reduce power to a resistive load. Some two position lamp dimmer switches apply full AC power to the lamp filament for “full” brightness and then half-wave rectify it for a lesser light output.

As the dominant capacitor technology in terms of component quantities, the Multilayer Ceramic Chip Capacitor’s (MLCC) popularity with circuit designers is principally due to its high reliability record and low cost. However, due to the nature of ceramic material the MLCC body can be liable to cracking if mishandled during assembly or used in extreme environments. For this reason cracking in an MLCC body is the most common mode of failure for PCB mounted MLCC components.