Wide-band current preamplifier for conductance measurements with large input capacitance
Abstract
A wide-band current preamplifier based on a composite operational amplifier is proposed. It has been shown that the bandwidth of the preamplifier can be significantly increased by enhancing the effective open-loop gain. The described 107 V/A current gain preamplifier had the bandwidth of about 100 kHz with the 1 nF input shunt capacitance. The measured preamplifier current noise was 46 fA/sqrtHz at 1 kHz, close to the design noise minimum. The voltage noise was found to be about 2.9 nV/sqrtHz at 1 kHz, which is in a good agreement with the value expected for the particular operational amplifier used in the input stage. By analysing the total produced noise we found that the optimal frequency range suitable for the fast lock-in measurements is from 1 kHz to 2 kHz. To obtain the same signal-to-noise ratio, the reported preamplifier requires ∼10% of the integration time needed in measurements made with a conventional preamplifier.
- Publication:
-
Review of Scientific Instruments
- Pub Date:
- August 2012
- DOI:
- 10.1063/1.4740521
- arXiv:
- arXiv:1204.2239
- Bibcode:
- 2012RScI...83h4704K
- Keywords:
-
- electric admittance measurement;
- electric current measurement;
- electric noise measurement;
- operational amplifiers;
- preamplifiers;
- wideband amplifiers;
- 84.37.+q;
- 84.30.Le;
- Measurements in electric variables;
- Amplifiers;
- Physics - Instrumentation and Detectors;
- Condensed Matter - Mesoscale and Nanoscale Physics
- E-Print:
- 5 pages, 4 figures