相關(guān)元件pdf下載：2n3904 7001 circuit notes 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 transists, audio gain limited by the 5k preset. the oscillat is a colpitts stage, frequency of oscillation governed by the tank circuit made from two 5pf capacits the induct. ( click here f colpitt oscillat resonant frequency equation.) frequency is around 100mhz with values shown. audio modulation is fed into the tank circuit via the 5p capacit, the 10k resist 1n4002 controlling the amount of modulation. the oscillat output is fed into the 3.9uh induct which will have a high impedance at rf frequencies. the output stage operates as a class d amplifier , no direct bias is applied but the rf signal developed across the 3.9uh induct is sufficient to drive this stage. the emitter resist 1k base resist prevent instability thermal runaway in this stage.