Ken Shirriff has written an article on reverse engineering a hybrid op amp module: I recently obtained a mysterious electronic component in a metal can, flatter and slightly larger than a typical integrated circuit.1 After opening it up and reverse engineering the circuit, I determined that this was an op amp built for NASA in […]
EMI reduction built-in on op amps, app note from Texas Instruments. Link here (PDF) Operational amplifiers (op amps) with electromagnetic interference (EMI) filters can reduce significant errors. These types of errors are not always obvious to the system designers. They often impact the signal chain, in particular the analog-to-digital converter in the form of a […]
Good read app note from Texas Instruments about configuring unused op amps on multi amp chips. Link here (PDF) Multi-channel operational amplifiers (op amps) are often implemented in circuits that do not require the use of all channels. Undesired behavior in an unused amplifier channel can negatively impact system performance, as well as the performance […]
Interesting app note from Silicon Labs on high efficiency charge pump utilizing their nanopower TS1001 op amp. Link here (PDF) Boosting the output voltage of common alkaline button-cells to at least 1.8 V needed by microcontrollers provides an “always on” standby power source sufficient for low-power oscillator interrupt/sleep state operation. Two ultralow power op amps […]
In this video, Kerry Wong examines how the clean/dirty circuitry from a Hoover vacuum cleaner works. Details at Kerry D. Wong blog.
A DIY ECG made from single op-amp (LM741) and 5 resistors by Scott Harden: I made surprisingly good ECG from a single op-amp and 5 resistors! An ECG (electrocardiograph, sometimes called EKG) is a graph of the electrical potential your heart produces as it beats. Seven years ago I posted DIY ECG Machine on the […]
In this video Craig shows how to build a window comparator with a single Op-Amp: A recent question on the Electrical Engineering Stack Exchange site got me thinking about some interesting window comparator circuits. Here’s how to detect three different input voltage levels with just one op-amp! More info at Analog Zoo site.
Ron Hoffman over at Gadgetronicx has written up an article on his DIY model train controller project: Model trains are fun toys which every one of us used to play with in our childhood. Many sophisticated and attractive model trains are available in the market now a days yet the basic principle in build a controller for […]
All about Op Amp stability app note from Linear Technology. Well, it shouldn’t. We analog designers take great pains to make our amplifiers stable when we design them, but there are many situations that cause them to oscillate in the real world. Various types of loads can make them sing. Improperly designed feedback networks can […]
Kerry Wong writes: Hysteresis can be added to a comparator circuit to improve its stability, especially when the input signal is noisy. In this post, we will examine the hysteresis characteristics of some common comparator and Op Amps using an oscilloscope. Perhaps the most intuitive way to visualize the hysteresis in a circuit is to […]
Davide Gironi writes: This is an op-amp Electret Condenser Microphone Preamp board design for the use with microcontrollers ADC. For the NPN version of this board, an for more information about microcontroller ADC and microphone input, please refer to this page The proposed circuit is just a revision of a pretty usually op-amp electret mic preamplifier. […]
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 […]
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 […]
Op amps needs dual supply in order to get a full output swing from its input fed signal, here’s a good app note from Analog Devices on powering op amps using only a single supply. Battery-powered op amp applications such as those found in automotive and marine equipment have only a single available power source. […]
This video by Analog Devices’ Matt Duff discusses the key term, loop gain, in determining whether an operational amplifier circuit is stable.
This video discusses the total noise of a non-inverting Operational Amplifier (Op Amp) circuit by Analog Devices’ Matt Duff.
Drone writes: Here is a nice little app-note that describes a quick test for op-amp stability using SPICE. (Actually the technique might be useful on the bench as well.) The approach involves applying a step directly to the op-amp input pin and observing the step response. The Author points out what to look for in […]
How to drive capacitive loads with op amps. Operational amplifiers that drive large capacitive loads can have problems like oscillation and peaking. This article describes how to anticipate and limit theses problems: Other problems include: reduced bandwidth, lower output slew rate, and higher power consumption. This application note explains why these problems occur, how to […]
This is not really an app note, but more of a tutorial on DIY op-amp based linear regulators. The article describes the basics of op-amp regulator, and includes schematics and in-depth explanations of how the various circuits work. This article follows the history of a popular series of DIY linear regulators. Starting from initial concepts […]
Here is a application guide from Texas Instruments is an overview of operational amplifier-related circuits, theory, and formulas. Inverting amplifiers, buffers, analog adders, filters, and many more are covered. The general utility of the operational amplifier is derived from the fact that it is intended for use in a feedback loop whose feedback properties determine […]