Difficulty with Common Emitter Amplifier

Posted on Feb 6, 2014

Take the input from a microphone and use it to power an LED, so that it`s off at ambient sound, and (the peak brightness) gets brighter with noise level. It`s okay if it flickers, I`m just trying to get the peak voltage to be proportional to sound levels. What I know: - The loudest sound I use causes the microphone to emit 80mV - The

Difficulty with Common Emitter Amplifier
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LED faintly lights at 1. 8 V - The LED maxes out at 2. 2 V - The transistor I`m using activates when V_be > 0. 6 V You show the microphone connected to a "ground" symbol, but you don`t show any other node in the circuit also connected to ground. This makes it difficult figure out what your intent is. The circuit would probably work if you connect it to the junction of R2 and RE. Dave Tweed™ Apr 17 `13 at 2:09 Alright, I`ve made the modifications that @DaveTweed and Peter Bennett mentioned, and now: the LED`s current varies at 440Hz, from 3. 84 to 4. 61 mA, and the voltage at the LED and capacitor vary very little (~10 mV per cycle). The voltage at the emitter is low, at max 930 mV. Hopefully this is enough information for troubleshooting. :/ I can link the simulator I`m using, if that helps Henry Swanson Apr 17 `13 at 2:34

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