o Types of Microphones: Condenser Microphones (used in telephones & recorders) use capacitors for audio transduction.
o Working of a Condenser Microphone: Contains a capacitor with two plates separated by a dielectric → One plate is replaced with a vibrating diaphragm → When sound waves strike the diaphragm, capacitance changes, generating an audio signal.
o Preamplifier (Preamp): Acquires the audio signal (voltage form) and boosts it using external power while minimizing noise → Gain = (Output/Input ratio) → Impedance matching is crucial to avoid signal noise.
o Amplification Process: Transistors are used as active components to amplify voltage.
o Bipolar Junction NPN Transistor: Has three terminals: Base, Collector, and Emitter.
o Small voltage at the base → triggers large electron flow from emitter to collector → generates high collector current.
o Collector supplied with high voltage → produces strong output voltage.
o Amplified Signal: Maintains the same waveform but with a larger voltage swing.
o Stages of Amplification: Driver Stage (Uses transistors to maintain voltage while increasing current) → Power Stage (Further increases both voltage & current before signal reaches the loudspeaker).