This circuit might also be of interest to people making pre-amps for electret and externally polarized condenser microphones which have no internal FET. (If a single FET`s noise is the limiting factor, perhaps two or four could be run in parallel. ) Some `two terminal` electret microphones can be modified to provide separate access to the Source an
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d Drain of the internal FET. This, together with a new arrangement for biasing the modified capsule, is known as the "Linkwitz modification" (Linkwitz mod) and was first developed, or at least first made widely known, by Siegfried Linkwitz : The test arrangements are not necessarily very accurate in terms of absolute sound levels - I was using a cheap sound meter. I guess they are accurate within a few dB SPL. The tests were purely of 1kHz at sound levels between 110 dB SPL and 140 dB SPL. I have not yet measured frequency response or background noise. Nor have I yet done any listening tests. They are 14mm in diameter. They are a "back electret" design with a layer of charged fluoropolymer (I assume) on the front of the backplate. The diaphragm is 3 um thick aluminized mylar (I assume) with the aluminization layer, which is grounded, on the front. At the back we have Ground, Source and Drain. For the capsule at the lower right of the above photo, the Ground is the gold-plated tracks, the Drain is to the upper left and the Source is to the lower right. The only access to the backplate we have is through the gate of the FET - so we have to do everything via the FET`s Source and Drain. We need to get to know this device as well as possible. This does not appear to be one of the FETs in current production at NEC. The current ones have rather similar specifications. Maybe this pre-amp design will work just as well with FETs...
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....
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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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