Current Feedback Amplifiers (CFB)

We often misunderstand current feedback amplifiers, although they have been available for many years!

Current Feedback (CFB) operational amplifiers (Op-Amps) have been around for more than 30 years. They were designed for extreme high-speed performance, which Voltage Feedback (VFB) amplifiers could not accomplish at that time. 

CFB amplifiers have one major advantage over VFBs, they maintain their bandwidth over a wide range of signal gain. Note that VFB amplifiers are gain-bandwidth dependent, meaning their bandwidth decreases with increasing signal gain.

In practice, CFB amplifiers are commonly used in high-speed applications while VFB amplifiers are preferably used in precision applications.

Now see the figures below (click image to enlarge):

A VFB amplifier has two symmetrical, high-impedance inputs. The fact that the negative input is high-impedance makes the feedback network, driven by the output voltage VO, operate in Voltage-Source mode.

Here the series source impedance of this voltage source is the parallel circuit of RF and RG. The output of this voltage source is connected to the inverting input, providing the voltage potential, vn, at this pin.

The voltage potential at the non-inverting input, vp, is identical to the signal input voltage VI. Thus, the difference between the two input potentials is an error voltage, ve, that is amplified to generate VO.

However, unlike the VFB amplifier, the CFB amplifier has asymmetric inputs. Internally the non-inverting input connects using a unity-gain buffer to the inverting input. Thus, the non-inverting input exhibits the high impedance of the buffer input, while the inverting input presents the low impedance of the buffer output to the feedback network.

This low input impedance makes the feedback network operate in Current-Source mode. The parallel source impedance of this current source again is the parallel circuit of RF and RG.

During normal operation, the input voltage VI drives a current, ip, into the non-inverting input, and the output of the feedback current source drives a current, in, into the inverting input. The difference between the two input currents is the error current, ie. This error current is driven into an internal high-impedance stage, which results in the output voltage, VO.

To summarize, the major difference between a VFB and a CFB amplifier is the type of input error signal generating the output voltage. A VFB op-amp uses an error voltage while a CFB op-amp uses an error current.

⇲ REFERENCE: RENESAS Application Note AN1993 Rev.0.00, May 31, 2018

OK, current feedback op-amps can be successfully used in a variety of applications. More to come later!

Intelligent Power Module (IPM)

Power semiconductor devices play a significant role in modern power control and drive systems, and one of the most common devices used in these systems is the IPM module.

An IPM (Intelligent Power Module) is in fact a powerful integrated circuit module used for controlling and driving high-power electronic devices such as AC motor drivers, inverters, frequency converters, etc. It is a highly integrated semiconductor device that typically includes multiple functional modules such as power switches, drive circuits, protection circuits, and control circuits.

So, IPM is an acronym for Intelligent Power Module, a general term for modules that combine discrete semiconductors such as IGBTs and MOSFETs with driving circuits, protection circuits, and other circuitry.

Since the driving conditions and protection functions are optimized for the built-in power devices, and because they are easy to use, they are called Intelligent Power Modules (IPMs),

Keep note at this point that the key difference between Power Modules and IPMs is that a power module incorporates multiple discrete semiconductors in a single package, but a driving circuit and a protection circuit must be provided separately.

That is, an IPM typically includes a power MOSFET, IGBT, or SiC(Silicon Carbide) switch device, as well as a drive circuit for controlling the conduction and cutoff of these switch devices.

In addition, IPM modules often integrate features such as power supply circuits, current and voltage sensors, over-temperature protection, and short-circuit protection.

These functions provide comprehensive protection measures to ensure the safety and reliability of high-power electronic devices.

As an example of a widely used IPM, here is the PDF DATASHEET ↗ of a 600V IGBT IPM.

The aforementioned IPM (BM63563S-VA/-VC) is an intelligent power module (3phase DC/AC Inverter) composed of gate drivers, bootstrap diodes, IGBTs, flywheel diodes. Low saturation voltage IGBTs optimized for low speed switching drive (to 6kHz) such as a compressor is adopted.

As an aside, the HSDIP25 is a long pin type package for intelligent power modules (IPMs). See this PDF ↗ for more IGBT-IPM details from ROHM Semiconductor.

To be continued ⪫⪫⪫

Audio Filters Guide

An audio filter is one of the most essential building blocks of audio electronics, and it is a processing technique used to manipulate sound signals in a specific manner.

An audio filter can modify the frequency response of an audio signal, change its tone or texture, remove unwanted noise or artifact, or enhance specific aspects of the audio. 

In essence, an audio filter is a hardware device or software program that is designed to filter the frequency characteristics of an audio signal. The basic idea behind a filter is exactly as it sounds - they filter some frequencies out, and let others remain. 

With audio filters, we can filter specific frequencies, or whole groups of frequencies, known as bands. You can see them everywhere in the audio world, but to use them, you have to know how they work, and which filters are best for each purpose.

First off note that there are many different types of audio filters, including low-pass filters, high-pass filters, band-pass filters, and notch filters, among others.

Each type of filter has its own unique characteristics and can be used for different purposes in audio processing.

⪫ A low-pass filter (LPF) is a type of audio filter that allows low frequency signals to pass through, but blocks or attenuates high frequency signals.

⪫ A high-pass filter (HPF) is a type of audio filter that allows high frequency signals to pass through, but blocks or attenuates low frequency signals.

⪫ A band-pass filter (BPF) is a type of audio filter that allows a specific range of frequencies (also known as a band) to pass through, while blocking frequencies below and above this range.

⪫ A band-stop filter is a filter that allows us to let everything pass, while selecting a band of frequencies to remove

⪫ A notch filter is a filter that allows us to remove or reduce a specific frequency (this is similar to the band-stop filter, but it focuses on a targeted frequency precisely).

In other words:

⪫ A low-pass filter passes low frequencies and cuts or filters out high frequencies.

⪫ A high-pass filter is useful to cut low frequencies, so it  is sometimes called a low cut ( the same way a low-pass is occasionally called a high cut).

⪫ A band-pass filter can be useful for isolating a particular range of frequencies in an audio signal, or for shaping the tonal character of a sound by boosting or cutting a specific range of frequencies.

⪫ A band-stop filter is the opposite of a band-pass filter.

⪫ A notch filter is similar to a band-stop filter. It is called a notch filter because it creates a notch (or dip) in the frequency response at the target frequency, effectively attenuating or cutting that frequency.

Now you’ll know what common audio filters are and how to use them.

Wikipedia https://en.wikipedia.org/wiki/Audio_filter

Well, stay tuned to get more helpful pointers for creatively shaping the tone of your sounds in sound design.

Spoiler Alert ⨶  There are thousands of ways you could apply audio filters creatively!

Reference Source - https://www.native-instruments.com/en/

Ring Radiator (Audio)

Ring Radiator is a radical revolution in domestic audio technology.

A ring radiator, also known as a ring speaker, is a type of tweeter that differs from traditional high-frequency transducer, which differs from the traditional dome loudspeakers.

Its distinctive design incorporates the utilization of a ring-shaped diaphragm in place of the conventional dome.

The design also allows for an even distribution of sound, which results in a more natural and detailed sound quality.

In Hi-Fi audio systems where sound quality is of primary importance, the ring radiator will prove to be an adequate solution.

It is a characteristic of traditional tweeters that they are prone to generate distortion at higher volume levels.

But the ring radiator’s distinctive design ensures minimal distortion, thus facilitating a more natural sound even at high volumes.

Thus, the capacity of the device to reproduce treble without distortion permits users to enjoy music of the highest quality.

Now see the Scan-Speak Ring Radiator Tweeters Datasheet PDF

The area of audio technology is perpetually engaged in an ongoing pursuit of excellence.

Audiophiles and those with a keen interest in audio and music are consistently seeking out equipment that will provide them with the optimal listening experience.

One of the most recent developments in this field is the ring radiator.

Here you will see an an article that examines the nature of a ring radiator, the advantages of utilizing such a device, and the reasons why a domestic audio system comprising one is capable of producing a superior audio experience which sounds better than ever before ↓

https://dioraacoustics.com/en/ring-radiator-a-radical-revolution-in-domestic-audio-technology/

Quick Guide to Trimmer Capacitors

This post is a quick guide to trimmer capacitors!

As you already know, trimmer capacitor is a variable capacitor which can be used to trim the performance of both active and passive circuits.

Trimmer capacitors typically cover a capacitance range of 1 pF to 2 pF but can extend up to 200 pF or more.

While a fixed capacitor is essentially two fixed metal plates that hold charge, in a trimmer capacitor the plates (the stator and rotator plates) are either adjusted in distance from each other or the amount of exposed area is shifted to change the amount of capacitance.

Also, like a fixed capacitor, some form of dielectric such as air, ceramic, glass, polytetrafluoroethylene, or sapphire is used as electrical insulation between the plates or other metalized surfaces.

Further Reading ↗ https://blog.knowlescapacitors.com/blog/your-quick-guide-to-trimmer-capacitor-selection-part-1

Note that there are a variety of trimmer types available. What is important is choosing the right one for each application.

Each of the trimmer capacitor types has its positive and negative aspects, and some are better suited to particular circuits than others. Understanding how to make the most of a trimmer capacitor involves an array of choices in packages, dielectric materials, and performance parameters.

Trimmers are available in precision Multi-Turn and Half/Single turn formats. Ceramic half-turn trimmers are the most common types as they are well suited to applications in which low cost and small size are the overriding concerns.

At higher frequencies, a multi-turn trimmer with Air, Teflon or Sapphire dielectrics provides the best solution. In an air trimmer, capacitance is created by a movable set of concentric metal rings fitted into a fixed set of parallel rings. As the rings mesh, capacitance increases. A fine-thread screw provides many turns of resolution for setting to the exact desired value.

Learn More ↗ https://www.mwrf.com/technologies/components/article/21846602/evaluating-trimmer-capacitor-choices

And see the datasheet of muRata TZC3 series ceramic trimmer capacitors in PDF

Fast Recovery Diode

A fast recovery diode (FRD) is a type of diode with a short reverse recovery time (Trr) that is used for high-frequency switching!

The structure and function of an FRD is the same as that of a rectifier diode.

Rectifier diodes are used for low-frequency applications below 500 Hz, whereas FRDs are used for high-frequency switching from a few kHz to 100 kHz.

Therefore, the reverse recovery time (Trr) of the diode characteristic, which is important for high-speed switching, is short. FRDs are also referred to as S-FRDs, HEDs, etc. according to the Trr value.

The trr of a general rectifier diode is several μs to several tens of μs. On the other hand, Trr of an FRD is several tens of ns to several hundred ns and is about 1/100 of that of the rectifier diode. It is used in switching power supplies, inverters, dc/dc converters, etc.

In other words, FRD is a diode with a p-n junction is designed to make the reverse recovery time (Trr) smaller and is also called a high-speed diode.

Compared to general rectifying diodes (standard recovery diodes), the Trr is 2 to 3 digits smaller because the FRD is designed with a switching power supply to rectify high frequencies of tens of kHz or hundreds of kHz.

So, FRD stands for fast recovery diode. Such a high-speed diode offers high-speed support and generally have a Trr of approximately 50 to 100 ns.

Note, with a VF (forward voltage) of approximately 1.5 V, it is rather large when compared to general rectifying diodes (the smaller the reverse recovery time is made, the larger the forward voltage becomes).

On the other hand, general rectifier diodes are low-speed p-n diodes with large trr and small VF. These diodes are designed for commercial frequencies such as 50/60 Hz, and are not used in fast switching circuits.

Even among the fast recovery diodes, Ultra Fast Recovery Diode is a component designed specifically for speed. In this case, the Trr is approximately 25 ns, which is extremely small, but the VF is quite large at 3 to 3.6 V.

Now see the PDF datasheet of the FR107 1A Fast Recovery Diode https://www.diodes.com/assets/Datasheets/products_inactive_data/ds26001.pdf

To sum-up, diodes can be subdivided into two main classes: Rectifier diodes (standard recovery) and fast diodes.

Rectifier diodes are generally used for conversion of alternating current to direct current (AC to DC). While optimized for low conduction losses, rectifier diodes withstand only moderate dynamic stress in transition from conducting to the blocking state.

Fast diodes, on the other hand, are companion devices to switches in DC to AC conversion. Fast diodes are optimized to accept high dynamic stress (fast transition from conducting to blocking state). However, they generally have higher conduction losses than rectifier diodes.

(thanks to https://www.shindengen.com/ , https://www.hitachienergy.com/in/en , &  https://www.global.toshiba/ww/top.html)

Kelvin–Varley Divider

Kelvin-Varley Voltage Divider, named after its inventors William Thomson, 1st Baron Kelvin and Cromwell Fleetwood Varley, is an electronic circuit used to generate an output voltage as a precision ratio of an input voltage, with several decades of resolution.

The Kelvin Varley Voltage Divider may be thought of as being equivalent to a digital potentiometer, except that it has an additional, variable resistance in series with the wiper arm (see the circuit model figure below).

In effect, the Kelvin–Varley divider is an electromechanical precision digital-to-analog converter, and it is used for precision voltage measurements in calibration and metrology laboratories. It can achieve resolution, accuracy and linearity of 0.1 ppm. 

The conventional voltage divider - Kelvin divider - uses a tapped string of resistors connected in series. The fundamental disadvantage of this architecture is that resolution of 1 part in 1000 would require 1000 precision resistors.

To overcome this limitation, the Kelvin–Varley divider uses an iterated scheme whereby cascaded stages consisting of eleven precision resistors provide one decade of resolution per stage.

Cascading three stages, for example, therefore permits any division ratio from 0 to 1 in increments of 0.001 to be selected. Each stage of a Kelvin–Varley divider consists of a tapped string of equal value resistors. See Wikipedia ↗

In practice, if you want 10 steps you need 11 resistors. But by placing a second resistor divider of 11 resistors over two resistors of the tap of choice of the first, you can divide that step into 10 steps again. 

So you already have a resolution of 100 steps with 22 resistors. In essence, you can continue like this infinitely and make incredibly small but also very precise steps. The last string is, what is called, a normal Kelvin Divider.

Below is the basic circuit of a 4-Decade Kevin-Varley Voltage Divider (click on image to enlarge).

Note that in a typical KVD design, each stage provides a decade of resolution and requires only 11 precision resistors. Cascading 3 stages permits any division ratio from 0 to 1 in increments of 0.001 (i.e. resolution of 1 part in 1000).

Now see the three-terminal, Kelvin-Varley Voltage Divider KVD-500 with thumbwheel switches suitable for use in voltage and current dividers for calibration and linearity testing.

Well, comments and corrections to our understanding are always welcome. See you soon!

Moisture Sensitivity Level (MSL) & Popcorn Effect

MSL (Moisture Sensitivity Level) is an electronic standard which is established by JEDEC for the time period in which a moisture sensitive device can be exposed to ambient room temperature.

That is, short for Moisture Sensitivity Level, MSL is a JEDEC (Joint Electron Device Engineering Council) standard established for the purpose of preventing device failure due to volumetric expansion of atmospheric moisture introduced into the resin package of semiconductor devices during reflow.

Note that a semiconductor components with resin-sealed package could be damaged during SMD reflow when moisture was trapped inside the component expands.

And, according to the aforementioned JEDEC standard, there are eight levels of moisture sensitivity as shown in the below table.

Simply put, Moisture Sensitivity Level (MSL) defines how sensitive components are to moisture. Lower MSL levels allow manufacturers a wider processing window; reducing inventory & processing costs.

Popcorn Effect: The popcorn effect is when an IC pops because the moisture inside the package expands in the reflow process. As a result of this expansion the substrate, the die, or the wire bonds could be damaged. 

Note that when the antistatic bag is opened and the IC is exposed to ambient conditions, the moisture in the air is trapped inside the device. This means that during the reflow process, this moisture expands and can damage the device. The damage is often invisible and requires X-ray equipment to conduct a proper analysis.

To avoid the Popcorn Effect, you can simply bake the device and seal it in a hermetically sealed antistatic bag. If the device was exposed to moisture, re-bake it and assemble the device within the allowed exposure time (the baking is driving all the moisture out of the device).

Next figure shows an Xbox 360 graphical processing unit that was desoldered from an Xbox 360 motherboard (https://commons.wikimedia.org/wiki/File:PopcornBGA.jpg).

This photograph shows the risks of desoldering ball-grid array components without proper procedures. 

Here you can see that moisture in the circuit board turned to steam when it was subjected to intense heat. This produces the so-called Popcorn Effect.

You can prevent this by using a fast-acting solvent such as methyl ethyl ketone as well as preheating the circuit board using an oven.

Well, we will be providing more updates in due course ⪫

Found an error? Something else is just not right? Let us know! Leave a comment below!

Banana Plugs Guide

Popular test instruments and test accessories such as leads and cables use banana connectors.

Banana plugs are spring-loaded, single-wire electrical test connectors used for joining wire to electrical equipment or electrical circuit boards.

A banana plug is considered a male connector and is called a banana because of its unique contact tip.

The banana plug is a cylindrical pin that has metal-leaves that bulge outward to produce a strong connectivity contact (snug fit) in a socket to prevent the pin from disconnecting or falling out.

Banana connectors come in two forms, a banana plug or a banana socket (often referred to as a banana jack).

From Wikipedia, a banana connector (commonly banana plug for the male, banana jack or socket for the female) is a single-wire (one conductor) electrical connector used for joining wires to equipment.

The term 4 mm connector is also used, especially in Europe, although not all banana connectors will mate with 4 mm parts, and 2 mm banana connectors exist. Various styles of banana plug contacts exist, all based on the concept of spring metal applying outward force into the unsprung cylindrical jack to produce a snug fit with good electrical conductivity. 

OK, as with all things, there are tons of banana plugs out there offering different combinations and styles or features used for testing equipment and other applications.

And, here is an E-Z HOOK guide to what those banana plug features are, when to use them, and which part is compatible for your specific testing requirements » https://e-z-hook.com/blog-guide-to-banana-plugs/