Free circuit schematics - wiparat.com

As simple as it gets. The mixer consists of two transistor-based preamplifiers. The first one (designated “Mike in”) offers higher gain. it works well with a regular dynamic microphone. The second one can be used to control audio input from a tape recorder/CD player. [...]
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Here’s a simple problem: “How do you make an LED turn on when it gets dark?” You might call it the “nightlight problem,” but the same sort of question comes up in a lot of familiar situations– emergency lights, street lights, silly computer keyboard backlights, and the list goes on.
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This circuit provides an FM modulated signal with an output power of around 500mW. The input
Mic preamp is built around a couple of 2N3904 transistors, audio gain limited by the 5k preset.
The oscillator is a colpitts stage, frequency of oscillation governed by the tank circuit made from
two 5pF capacitors and the inductor. [...]