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Published on: January 4, 2011
Wide-band current preamplifier for conductance measurements with large input capacitance
Andrey V Kretinin1, Yunchul Chung
1Condensed Matter Physics Department, Weizmann Institute of Science, Rehovot, Israel.
The Review of Scientific Instruments
|September 4, 2012
Summary
This study introduces a wide-band current preamplifier that significantly boosts bandwidth by enhancing open-loop gain. The new design offers improved noise performance and reduces measurement time for fast lock-in applications.
Area of Science:
- Electronics
- Instrumentation
- Signal Processing
Background:
- Conventional current preamplifiers often face limitations in bandwidth and noise performance.
- Enhancing operational amplifier open-loop gain is a key strategy for improving preamplifier characteristics.
Purpose of the Study:
- To propose and characterize a wide-band current preamplifier utilizing a composite operational amplifier.
- To demonstrate significant bandwidth enhancement through effective open-loop gain increase.
- To evaluate the noise performance and suitability for fast lock-in measurements.
Main Methods:
- Design of a composite operational amplifier-based current preamplifier.
- Measurement of preamplifier bandwidth with specified input capacitance.
- Characterization of current and voltage noise spectral densities.
- Analysis of noise contributions to determine optimal operating frequencies.
Main Results:
- Achieved a current gain of 10(7) V/A with a bandwidth of approximately 100 kHz at 1 nF input capacitance.
- Measured current noise of 46 fA/√Hz at 1 kHz, near the design minimum.
- Measured voltage noise of 2.9 nV/√Hz at 1 kHz, consistent with the input stage operational amplifier.
- Identified an optimal frequency range of 1 kHz to 2 kHz for fast lock-in measurements.
Conclusions:
- The proposed composite operational amplifier design significantly enhances preamplifier bandwidth.
- The preamplifier exhibits low noise performance, suitable for sensitive measurements.
- The developed preamplifier offers a substantial reduction in integration time (~10%) for achieving equivalent signal-to-noise ratios in fast lock-in measurements.
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