The opamp Wien-bridge oscillator provides a nice view into classic oscillator design using feedback analysis. Feedback analysis reveals if your circuit is stable (well behaved) or unstable (may oscillate). When designing amplifiers (especially high-speed ones), the trick is to avoid the conditions that make the circuit oscillate. When designing os
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cillators, you strive to achieve those conditions in a predictable way. Feedback analysis simply means opening the circuit and injecting an AC signal VTEST at one end of the circuit. Then, by looking at the magnitude (gain) and phase (time-shift) of signal as it travels around the opened loop, you can tell whether you`ve got an amplifier or an oscillator on your hands. When wearing your oscillator design hat, the idea is to pick components that will make the open-loop analysis meet the conditions for oscillation at your chosen frequency: The conditions are as follows: Open the loop of the Wien Bridge Oscillator at the op amp`s output. This is a good point because of the relatively low impedance of the output terminal. Likewise, VTEST also has a low output impedance. Therefore, opening the loop here does not significantly alter the circuit`s behavior. Two basic sections form the Wien-bridge oscillator: an RC tuning network and an amplifier. Both are necessary to achieve the conditions for oscillations. The RC network is characterized by a center frequency where R=R1=R2 and C=C1=C2. At the center frequency, two interesting things occur at V(3). First, the phase shift goes through 0 degrees. And second, the magnitude reaches a peak of 1/3 V/V. CIRCUIT ANALYSIS Run a SPICE simulation of the open-loop circuit OPWEIN_OL. CIR. Add trace VM(3) to see what the Magnitude looks like at the center frequency. For R1=R2=10k and...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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