Description: The model 181 is a current-to-voltage preamplifier of low noise and low input impedance designed to amplify the extremely low low currents encountered in such areas as photometry and semiconductor research. In photometric applications the low input noise allows the use of photodetectors with dark currents as low as 10-14 A/root Hz, while the wide frequency range permits high modulation frequencies to avoid 1/F noise and power-line pick-up.
The unit has a high dynamic range, allowing small AC currents to be amplified without overload in the presence of quiescent (DC) detector currents up to ten times the current to voltage converter setting. In semiconductor applications its low input impedance permits the actual bias voltage applied to the device under test to be measured without having to correct for the effects of back bias.
Six switch-selectable gain settings from 10-4 A/V to 10-9 A/V are available and the instrument has a useable frequency range from DC to 200 kHz. A signal monitor connector is provided on the rear panel and there is an overload indicator light on the front panel.
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