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Ultra-low-noise preamplifier for condenser microphones.

Tomasz Starecki¹

¹Institute of Electronic Systems, Warsaw University of Technology, 00-665 Warsaw, Nowowiejska 15∕19, Poland. tomi@ise.pw.edu.pl

The Review of Scientific Instruments

|January 5, 2011

Summary

This study introduces a novel low-noise preamplifier for high-sensitivity condenser measurement microphones. The design significantly reduces noise, improving measurement sensitivity at low frequencies compared to existing instruments.

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Area of Science:

Electrical Engineering
Acoustics
Instrumentation

Background:

Amplifier noise is a primary limitation in high-sensitivity measurement microphone applications.
Bias resistance in the input stage is a dominant noise source at low frequencies for measurement microphone preamplifiers.

Purpose of the Study:

To design and present a low-noise preamplifier for condenser measurement microphones.
To overcome the sensitivity limitations imposed by amplifier noise in high-sensitivity measurements.

Main Methods:

The preamplifier design incorporates input stage resistors connected via switches.
Resistors are disconnected during measurement to reduce noise.
Switches are closed for rapid charging of microphone capacitance.

Main Results:

The designed preamplifier exhibits significantly lower noise at low frequencies.
Noise levels are several times lower than comparable commercial instruments.
The novel switching technique effectively minimizes bias resistance noise.

Conclusions:

The developed low-noise preamplifier enhances measurement sensitivity for condenser microphones.
The switching method offers a practical solution for reducing low-frequency noise in preamplifiers.
This design represents an advancement in instrumentation for high-sensitivity acoustic measurements.