App note: Thermal management in surface-mounted resistor applications

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App note from Vishay on PCB thermal management specifically on components like SMD resistors, where if allowed a design change (e.g. change in SMD size or change in more heat tolarant ones) must be implemented in order to squeeze more thermal capability. Link here (PDF)

Thermal management is becoming more important as the density of electronic components in modern printed circuit boards (PCBs), as well as the applied power, continues to increase. Both factors lead to higher temperatures of individual components and of the entire assembly. However, every electrical component in an assembly has to be used within its prescribed operating temperature limits due to its material properties and reliability aspects. In this application note, experimental results are provided in order to prevent overheating of electronic devices such as surface-mount resistors.

App note: Minimizing the temperature dependence of digital potentiometers

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Application notes from NIDEC COPAL Electronics Corp. about digital potentiometer’s temperature dependence. Link here (PDF)

The digital potentiometers (DP) has two temperature dependent parameters, the TC of the end-to-end resistance Rpot and the ratiometric TC. The temperature dependence of the parameters of an analog circuit using a digital potentiometers is reduced if the performance of the circuit is shifted from the TC of the end-to-end resistance of the pot to the ratiometric TC.

App note: Potentiometers and trimmers

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App note from Vishay on variable resistors primer. Link here (PDF)

A potentiometer is a mechanically actuated variable resistor with three terminals. Two of the terminals are linked to the ends of the resistive element and the third is connected to a mobile contact moving over the resistive track. The output voltage becomes a function of the position of this contact. Potentiometer is advised to be used as a voltage divider.

App note: How RF transformers work and how they are measured

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Application note from Mini-Circuits about transformers, this time the RF transformers. Link here (PDF)

RF transformers are widely used in electronic circuits for
* Impedance matching to achieve maximum power transfer and to suppress undesired signal reflection.
* Voltage, current step-up or step-down.
* DC isolation between circuits while affording efficient AC transmission.
* Interfacing between balanced and unbalanced circuits; example: balanced amplifiers.

App note: Transformers

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App note from Mini-Circuits on transformer types and some basics of them. Link here (PDF)

The purpose of this application note is to describe the fundamentals of RF and microwave transformers and to provide guidelines to users in selecting proper transformer to suit their applications. It is limited to core-and-wire and LTCC transformers.

 

App note: Selecting a FET for use with the Si875x driver

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Another application note from Silicon Labs on determining the proper FET used on their Si875x driver based on its application. Link here (PDF)

The Si875x enables creating custom solid state relay (SSR) configurations. Supporting customer-selected external FETs, the Si875x combines robust isolation technology with a FET driver to form a complete, isolated, switch. Versatile inputs provide digital CMOS pin control (Si8751) or diode emulation (Si8752) to best suit the application, plus flexible outputs to support driving ac or dc load configurations. A floating secondary side dc voltage source is unnecessary as the product generates its own self contained gate drive output voltage, reducing cost, size, and complexity.

App note: Driving MOSFET and IGBT switches using the Si828x

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App note from Silicon Labs on their MOSFET and IGBT driver Si828x and how to determining its external components to achieve optimized performance. Link here (PDF)

The Si828x products integrate isolation, gate drivers, fault detection protection, and operational indicators into one package to drive IGBTs and MOSFETs as well as other gated power switch devices. Most Si828x products (except the Si8286) have three separate output pins to provide independent rise and fall time settings and low impedance clamping to suppress Miller voltage spikes. This application note provides guidance for selecting the external components necessary for operation of the driver. Although this application note discusses the topic of driving IGBTs and MOSFETs, users can apply the same concepts for driving other gate-based power switches, such as SiC (Silicon Carbide).

App note: Gate drive characteristics and requirements for HEXFET power MOSFETs

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App note from International Rectifier on driving their Power MOSFETs. Link here (PDF)

The conventional bipolar transistor is a current-driven device. A current must be applied between the base and emitter terminals to produce a flow of current in the collector. The amount of a drive required to produce a given output depends upon the gain, but invariably a current must be made to flow into the base terminal to produce a flow of current in the collector.

The HEXFET®is fundamentally different: it is a voltage-controlled power MOSFET device. A voltage must be applied between the gate and source terminals to produce a flow of current in the drain. The gate is isolated electrically from the source by a layer of silicon dioxide. Theoretically, therefore, no current flows into the gate when a DC voltage is applied to it though in practice there will be an extremely small current, in the order of nanoamperes. With no voltage applied between the gate and source electrodes, the impedance between the drain and source terminals is very high, and only the leakage current flows in the drain.

App note: Microcontroller Clock – crystal, resonator, RC Oscillator, or silicon oscillator?

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App note from Maxim Integrated on clock sources of microcontrollers and their strengths and weaknesses. Link here

The majority of clock sources for microcontrollers can be grouped into two types: those based on mechanical resonant devices, such as crystals and ceramic resonators, and those based on electrical phase-shift circuits such as RC (resistor, capacitor) oscillators. Silicon oscillators are typically a fully integrated version of the RC oscillator with the added benefits of current sources, matched resistors and capacitors, and temperature-compensation circuits for increased stability.