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20 Aug 2014


Open Analog is an organization dedicated to exciting makers about analog hardware. We make popular ICs into transistor level kits!

 The first Open Source analog IC kit from Open Analog has been created, assembled, and verified. We call it the SevenFortyFun and it is a transistor level op amp kit. You can finally get the chance to understand whats going on inside those ICs! Now we need your help to proto the next revision (I gotta eat somehow!). This Kickstarter campaign is to raise money in order to print the first batch of PCBs and order parts for production volume.

741 Op-Amp Kit - [Link]

13 Aug 2014


Warren Young of Tangentsoft writes:

Experienced audio DIYers are familiar with monolithic linear regulators like the 78xx series and the LM317. Here’s a simplified block diagram of a standard linear regulator, from National Semiconductor’s Application Note 1148

Let’s see… We have an op-amp, a couple of transistors, a voltage reference, and a few resistors. Can we build a linear regulator from these individual components? Yes, we can!


Op-Amp based linear regulators - [Link]

15 Jul 2014


An application note from Texas Instruments, A single-supply Op-Amp circuit collection (PDF!):

There have been many excellent collections of op-amp circuits in the past, but all of them focus exclusively on split-supply circuits. Many times, the designer who has to operate a circuit from a single supply does not know how to do the conversion.
Single-supply operation requires a little more care than split-supply circuits. The designer should read and understand this introductory material.


A single-supply Op-Amp circuit collection - [Link]

6 May 2014


by Roy McCammon:

The traditional three op-amp differential amplifier’s signal to noise ratio can be improved by 6dB by adding a resistor and slightly changing the connections. There is a trade-off though: The traditional topology has a high input impedance, whereas the low-noise version has a lower input impedance.

Differential amp has 6dB lower noise, twice the bandwidth - [Link]

5 May 2014


by Kalle Hyvönen:

Every once in a while I’d have needed a function generator but since I didn’t have one I always had to resort to some sort of quick and poor 555 kludge or something similar. I spotted a nice looking DDS (Direct Digital Synthesis) kit meant for the Juma RX-1 receiver that uses the AD9833 DDS chip. I figured I should be able to use it as a function generator because the frequency range looked pretty nice (0-8MHz in 10Hz, 100Hz, 1kHz or 100kHz steps) for my needs.

I ordered and built the kit and got it running easily, next thing I had to do was to design and build an output amplifier for the DDS board because the output was just around 250mV peak-to-peak. I wanted around 5V peak-to-peak (p-p) out so for the first revision I just built a simple non-inverting op-amp amplifier with an AD847 op-amp and +-5V supplies and a gain of 25. The +-5V supplies were generated with a 78L05 regulator and a ICL7660 charge pump from a single supply. It did not work too well because the opamp was too slow for a gain of 25, so I got massive attenuation at higher frequencies.

DDS Function Generator - [Link]

14 Apr 2014

w2aew @ youtube.com writes:

A tutorial on the basics of an inverting and non-inverting summing amplifier using an op amp. The video assumes a basic knowledge of how inverting and non-inverting amplifiers using op amps work. If you are unfamiliar with this, I’d recommend viewing my video on how to easily understand the operation of most opamp circuits: https://www.youtube.com/watch?v=K03Rom3Cs28

Basics of an Op Amp Summing Amplifier - [Link]

5 Mar 2014

This tutorial discusses some general rules of thumb that make it easy to understand and analyze the operation of most opamp circuits. It presents some ideal properties of opamps, and discusses how negative feedback generally causes the input voltage difference to be equal to zero (input voltages are made equal by the action of negative feedback). In other words, the output will do whatever it can to make the input voltages equal. Applying this simple fact makes it easy to analyze most opamp circuits.

Basics of Opamp circuits – a tutorial on how to understand most opamp circuits - [Link]

4 Feb 2014


The LT6015 is a single Over-the-Top operational amplifier with outstanding precision over a 0V to 76V input common-mode voltage range. It incorporates multiple built in fault tolerant features, resulting in no-compromise performance over wide operating supply and temperature ranges. Over-the-Top inputs provide true operation well beyond the V rail. The LT6015 functions normally with its inputs up to 76V above V-, independent of whether V+ is 3V or 50V. Input offset voltage is 80μV max, input bias current is 5nA and low frequency noise is 0.5μVP-P, making the LT6015 suitable for a wide range of precision industrial, automotive and instrumentation applications. Fault protection modes guard against negative transients, reverse battery and other conditions. The LT6015 is available in a 5-lead SOT-23 package and is fully specified over -40°C to 85°C, -40°C to 125°C, and -55°C to 150°C temperature ranges.

LT6015 – 3.2MHz, 0.8V/μs Low Power, Over-The-Top Precision Op Amps - [Link]


22 Jan 2014

This article describes how to use infra-red (IR) sensor with Arduino or with a simple OPAMP comparator. Lee Zhi Xian writes:

What is infra-red (IR)? Infra-red is an electromagnetic wave who wavelength is between 0.75 microns to 1000 microns (1 micron = 1µm). Since infra-red is out of visible light range, we can’t really see IR with naked eye. However, there is a method to “see” IR which will be shown later on. Some of the infra-red applications includes night vision, hyperspectral imaging, and communications. We also use IR daily in our TV remote or any device remote.

IR transmitter and receiver can be obtained at low price. Their shape is looks exactly the same as LED. To distinguish between transmitter and receiver, the transmitter always come in clear LED while receiver is black in colour. Other than that, there is also receiver that is used to pick up specific frequency IR, 38kHz. For your information, 38kHz frequency IR is commonly used in remote control.

How to use infra-red (IR) sensor with Arduino - [Link]

14 Nov 2013

active_filter_designBy Bonnie Baker

Active analog filters can be found in almost every electronic circuit. Audio systems use filters for frequency-band limiting and equalization. Designers of communication systems use filters for tuning specific frequencies and eliminating others. To attenuate high-frequency signals, every data acquisition system has either an anti-aliasing (low-pass) filter before the analog-to-digital converter (ADC) or an anti-imaging (low-pass) filter after the digital-to-analog converter (DAC). This analog filtering can also remove higher-frequency noise superimposed on the signal before it reaches the ADC or after it leaves the DAC. If an input signal to an ADC is beyond half of the converter’s sampling frequency, the magnitude of that signal is converted reliably; but the frequency is modified as it aliases back into the digital output.

Designing active analog filters in minutes - [Link]





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