Electronics > Beginners

Adding power LED to circuit

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Mp3:
Here is the circuit i am building..



Should i put my LED between "Vin" and the point labeled "g"? I am thinking i should place a current limiting resistor after "Vin" and attach the LED to that. Is there anything wrong with that? This is going to be a small amplifier for a small microphone, so i'd rather not place the LED somewhere it might add needless noise to the circuit.

Ysjoelfir:
If you add it between Vin and the Gate of the JFET you will load your microphone with the LED and clip the signal to the leds voltage, which is a big no no.
Why don't you place it parallel to vdd with an apropriate sized resistor, if you want a power LED?

If you want an activity LED, which I assume you want when you place it directly parallel to the "amplifiers" input, you would need an amplifier for the activity LED, (could be as simple as an comparator which toggles over a certain threshold) as the voltages from a standard microphone are very, very, very low and would never turn on the led.

Also, I hope that your schematic is just an aproximation and not the real amplifier you are trying to build? If not think again about your design, this way it won't really work.

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