Published:2011/8/8 0:23:00 Author:Sophia | Keyword: Computer Microphone, JFET-MOSFET earphone, power amplifier | From:SeekIC
PC sound card usually possesses microphone input and loudspeaker output, sometimes line input and output. The design of input resistance of dynamic microphone just can be achieved in the scope of 200~600ohms. Sound card can use a common electret microphone to suit this curcuit. a composite amplifier can use two transistor.
when BC413B is working normally, it slightly drives the microphone signal emitter amplifier, next, it comes to the stage of emitter follower, which is necessary. Because that the microphone, curcuit and battery make use of the distance of some sound card, the low output resistance of circuit and shielded cable can ensure to collect the clean signal through the smallest noise pickup.
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