It simply amplifies the input signal and produces gain according to the equation (1). The potential divider biased circuit is shown in figure 1. Gain Stage: The gain stage uses a potential divider biased mosfet amplifier circuit. To achieve this the following stages were employed in the amplifier:ġ. GAIN OF THE CIRCUIT: The first objective is to attain a considerable power gain that is sufficient to give a noise free audio signal at the output through speakers. The specifications of the amplifier include: Gain and power stage is employed in the design to attain the required gain and bandwidth. The amplifier presented here uses mosfets to achieve the desired specifications of an audio amplifier.

Other applications include instrument amplifiers such as guitar amplifiers, professional and amateur mobile radio and portable consumer products such as games and children’s toys. The sound card in a personal computer, every stereo system and every home theatre system contains one or several audio amplifiers. Applications for audio amplifiers include home audio systems, concert and theatrical sound reinforcement and public address systems. Whereas, now-a-days transistor-based amplifiers are used that are lighter in weight, more reliable and require less maintenance than tube amplifiers. Early audio power amplifiers were based on vacuum tubes. The triode vacuum amplifier was used to make the first AM radio. The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The audio amplifier was invented in 1909 by Lee De Forest when he invented the triode vacuum tube (or 'valve' in British English). This includes both amplifiers used in home audio systems and musical instrument amplifiers like guitar amplifiers. 'An audio power amplifier (or power amp) is an electronic amplifier that strengthens low-power, inaudible electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is strong enough for driving loudspeakers or headphones.'

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