The first choice is usually an integrated circuit designed for the purpose. A typical assortment can be seen on this National Semiconductor page. Discrete designs can also be built with readily available transistors or op-amps andmany designs are featured in manufacturers` application notes. Older designs employed audio interstage and output transformers but the cost
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and size of these parts has made them all but disappear. (Actually, when the power source is a 9 volt battery, a push-pull output stage using a 500 ohm to 8 ohm transformer is more efficient than non-transformer designs when providing 100 milliwatts of audio. ) As a general rule, transformerless low power speaker projects will work better with 4. 5 or 6 volt battery packs of AA, C, or even D cells than 9 volt rectangulars. This simple amplifier shows the LM386 in a high-gain configuration (A = 200). For a maximum gain of only 20, leave out the 10 uF connected from pin 1 to pin 8. Maximum gains between 20 and 200 may be realized by adding a selected resistor in series with the same 10 uF capacitor. The 10k potentiometer will give the amplifier a variable gain from zero up to the maximum. The Curiously Low Noise Amplifier takes advantage of the wonderful noise characteristics of the 2SK117 JFET that boasts a noise voltage below 1 nV/root-Hz and virtually no noise current. The noise voltage of the amplifier is only 1. 4 nV/root-Hz at 1 kHz, increasing to only 2. 7 nV/root-Hz at 10 Hz. The noise current is difficult to measure, so this simple utility amplifier can see the noise from a 50 ohm resistor and a 100k resistor, too. (The 1. 4 nV input-referred noise will increase to about 1. 7 nV with a 50 ohm resistor, instead of a short, and a 100k resistor will give an input-referred noise near 40 nV, with very little contribution...
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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