Electronics is Fun

Ever saw an op amp circuit oscillating and behaving weirdly? We basically have just two options: give up to the idea it's not really going to work and try another circuit, or the better option would be is to figure out what is wrong and make it work. As some well known author has said, every op amp sits there waiting to oscillate [1]. I discussed in one of my articles here, titled What's The Feedback Around Op Amp All About?, the concept of negative feedback and how the large open loop gain makes the overall closed loop gain stable and predictable. It is when this negative feedback becomes not negative anymore, that is, if it becomes positive, that the circuit becomes unstable and starts to oscillate. Figure 1 General Feedback Topology How can that possibly happen? To put it in simplest terms, it happens when enough phase shift is introduced in the complete feedback path which includes the amplifier itself, enough to make the feedback turns180 degrees around, thus ma

This is the last installment of the grounding series articles I have posted. In Part II of this series, we have explained that star ground provides a single or common reference point to a circuit in an effort to avoid sharing of paths that could cause errors and degrade the integrity of the signals. This is accomplished by selecting a single "mecca" point where all ground return paths meet, and that this point should be a low impedance node. But this scheme is not always practical and doesn't solve all the woes of circuit grounding. Long routes going to the mecca point can itself be a source for error as it becomes inductive to high frequency signals. The rule of keeping the routes or wires as short as possible applies to grounding as well. The other scheme that we have described is the use of ground plane, because it presents much lesser resistance and inductance compared to the individual wires and traces. But we have cautioned that there are two paths the signal

Early this year I got my Digilent Analog Discover Kit . It is a wonderful PC based design and experiment kit complete with software measurement and resource tools perfect for students and professionals alike, but students surely will benefit the most out of it.The complete Discovery kit includes many useful exciting components that will enable you  to design your own circuit in your living room! One cute little component it has is the AD654 , a low-cost IC voltage-to-frequency converter. It is a very simple to use IC that outputs a square wave with programmable frequency, set by just a single RC network. The scaling relationship as obtained from its datasheet is: Below is a simple V-F circuit that takes its input from another IC included in the kit, the AD584 , a precision programmable voltage reference. Figure 1 V-F Converter The AD654 accepts full-scale current up to 2mA, but the best linearity is offered at 1mA full-scale. The voltage input is converted to a dr

Building circuits whether on a PC (Printed Circuit) board or a breadboard, grounding have always been important. Careful grounding becomes critical on applications where performance and integrity of the signals are of prime importance. Examples are low-level application such as in audio, in precision sensing and measurement circuits, and in mixed analog and digital circuits . When do we use star ground and ground plane? What is the difference between the two? Which is actually better? We will try to answer first what the difference between the two is. Star Ground Also sometimes called mecca ground, this is based on the concept of creating a single return point in the circuit as a common reference in order to avoid ground loops and thus circuit errors (See figure 1 [1]). In the figure, we could see the input signal return path is shared, assuming very high input impedance and no significant current flowing in it. Those in the path of significant current flow, such as the power supp