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 plot the input signal (x axis) against the output signal (y axis). So, if we sweep the input voltage we should be able to see the characteristics of the transitioning of the output voltage due to hysteresis.
Visualizing comparator and Op Amp hysteresis - [Link]
by Barry Harvey @ edn.com:
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 cause instability. Insufficient supply bypassing can offend. Finally, inputs and outputs can oscillate by themselves as one-port systems. This article will address common causes of oscillation and their remedies.
Does your op amp oscillate? - [Link]
An app note on Gamma-photon radiation detector (PDF) by Maxim:
A PIN photodiode, four low-noise op amps and a comparator are used to detect individual photons of gamma radiation. The schematic, design considerations and component selection are discussed.
Gamma-photon radiation detector - [Link]
by w2aew @ yoututbe.com
Op amp gain-BW product and slew rate limiting are defined, discussed and demonstrated on the bench. This discussion applies to the majority of general purpose op amps on the market – as most op amps are internally compensated with a single dominant pole. High speed op amps, unconditionally stable op amps, non-unity gain stable op amps, high power opamps, etc. may not follow these characteristics because they are often compensated differently in their design. An LM358N is used for the example circuit. Other popular op amps like the LM741, etc. will behave in a similar way. Sometimes the slew rate limit of a device will be the dominant factor in determining the bandwidth, and other times the gain-bandwidth product will determine the resulting frequency response. The video demonstrates why this happens.
Basics of Op Amp Gain Bandwidth Product and Slew Rate Limit - [Link]
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]
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]
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]
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]
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]
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]