While extracting weak signals, with compromising the intrinsic signal to noise ratio (SNR), from microphones, audio sources, and other sound detectors and fed to Power Amplifiers for further processing some small amplification is needed. Such one stage is called Preamplifier stage.
Usually Preamplifier stage amplifies the signal with very high gain and such boosted signal's current is amplified by next stage, i.e., Power Amplifier stage. As name implies Preamplifier stage comes before output driving Power Amplifier stage and after Audio source.
One more scenario is, circuit may contain filtering stage with audio source and which may add noise to the signal. And Power Amplifier stage may be at a distance from audio source. In such conditions also Preamplifier stage comes into action, and minimizes the noise of the whole circuit efficiently.
In Audio circuits volume control is done at the Preamplifier stage and gain is kept constant at output stage i.e., at Power Amplifier stage.
Types of Preamplifiers: current sensitive, charge sensitive and parasitic capacitance for different sensors, detectors.
Objective: In this project, a preamplifier is designed for an electret microphone with mono output, as seen in headphone/phones. For driving the headphone one Audio Amplifier stage is added.
The input signal is taken from electret microphone or phone output is considered for further processing.
The Op-Amp IC LM358 is used to construct Preamplifier stage in negative feedback manner with high value potentiometer for gain control.
The inverting end is connected with microphone and other non-inverting end is with a voltage divider circuit for constant input.
The Audio Amplifier stage is built using LM380 IC, and whole circuit works with 9 volts power supply. The output of Preamplifier stage is given to inverting terminal of Audio IC and its inverting pin is grounded. The output of Audio IC is filtered, and is given to speaker.
Applications:
Usually Preamplifier are weak in signal strength hence used only with particular audio outputs viz., microphone preamplifier, music recording studios, television antenna etc.
Title: LM358 Based Microphone Preamplifer System
External Links: electronicshub.org
- How To Make Microphone Preamplifier?
Keywords: LM358, LM380, Audio Amplifier, Preamplifier
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…till next post, bye-bye & take care.
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