Amplifiers and Sound Amplification

6. Amplifiers and Sound Amplification: It is used in entertainment, astronomy, search & rescue, medical diagnostics, and various fields converting physical changes into electric signals.
  • About Microphone: A transducer that converts sound waves into electrical signals.

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.

  • How Sound is Amplified?

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.

  • Voltage Amplification via Transistors

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).