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Power Resistor Derating For High Temperature

In complex electronic systems, the issue of power resistor derating for high temperature can often be overlooked. The system designer may have many design issues to consider and passive components, like an application specific power resistor, are often the last to be evaluated, if at all. It can, therefore, be quite late in the design phase that the designer realises that a standard resistor will not suffice and an application specific power resistor is required.

Advantages of A Resistor Network vs Discrete Devices

In many electronic systems discrete resistor devices are more than adequate but when reliability and performance are of prime concern and space is limited a resistor network can be a better choice. Resistor networks offer a number of advantages including: 
• Space Saving.
• Reduced resistor drift due to temperature and power variations.
• Lower cost.
• Improved System reliability.
Each of these issues is considered in more detail below.

High Voltage Resistor Applications

High voltage resistors are used in a wide range of applications including Power supplies, ESD protection, Electron Microscope, Air Ionising equipment, RADAR equipment and ATE. They tend to be used in high voltage bleeder, voltage balancing and voltage divider circuits. In this post, we discuss the key issues affecting the choice of a resistor in each circuit type.

Thick Film Power Resistor Mounting Considerations

Inappropriate thick film power resistor mounting can severely compromise the resistor performance. In this post, we cover the key points to consider

Position on System Board

As current passes through a resistor it generates heat that in turn induces stresses in the power resistor device as a result of differential thermal expansions of the resistor materials. This heat must be dissipated or the resistor performance and/or its lifetime will be compromised.

Power resistor ESD sensitivity

The most common cause of power resistor ESD damage is a direct transfer of an electric charge from either a human body or a charged material to the power resistor device. ESD damage may be divided into three main categories

1.       Parametric failure

The ESD event alters the resistance of the power resistor device causing it to shift outside its specified tolerance

2.       Catastrophic Damage

The Difference Between Pulse Power and Pulse Voltage Resistors

Pulse voltage resistors and pulse power resistors are employed as simple surge protection elements in many electrical circuits. A key design decision is the choice between pulse voltage resistors and those capable of withstanding a high current as the design of one is the exact opposite of the other. For pulse current handling the width of the resistive element is maximised but for high voltage pulses, it is designed to be long and narrow.

Pulse Handling Resistor Design

Using Resistor Networks In Matched Resistor Applications

Matched resistors are utilized in many applications including sensors for commercial, medical and military markets and pulse squaring elements. However, the most common applications is resistor divider circuits for amplifier applications. This article focusses on how to avoid amplifier output errors and discusses the merits of using resistor networks instead of discrete devices.

High Voltage Resistor Design Considerations

If a high voltage resistor is to perform to specification over an extended period of time there a number of design factors to consider. In this post we cover thick film resistor construction and the impact on performance of external thermal and mechanical issues.

Thick Film v Wirewound Power Resistors – A Comparison

There are many power resistor technologies available but the most common are Wirewound and Thick Film with other technologies reserved for specialist applications

Power Resistor Design Considerations

For any resistor technology, the four main design considerations are:

-Resistance value

-The resistor power handling capability

-The change in the resistance value over time

-The change in the resistance value with temperature

Passive Electronic Component Obsolescence Solutions

Resistors and other passive electronic components can often become difficult to source or obsolete at short notice causing delays to production schedules, upsetting important customers and wasting resources. Often, an attempt may be made to purchase residual stock from distribution or component brokers but this can lead to issues with quality or counterfeit components. As many manufacturers may be chasing the same solution the correct component can be both difficult and expensive to source.

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