GENERAL The Model 427 Current Amplifier is a high-speed, feedback-type amplifier with particular features useful for automated semiconductor testing, mass spectrometry, and gas chromatography applications. FEATURES. a. Wide Dynamic Range. Selectable rise times permit low-noise operation important when resolving small current levels. b. High Speed. Typical resolution is 20 picoamperes out of a 10⁻⁸ ampere signal with a 100 microsecond rise time. c. Built-in Current Suppression. Small changes in the signal level can be measured since large ambient current levels can be easily suppressed. d. Overload Indication. Accurate measurements are assured since overloads are automatically indicated. e. Variable Gain. The GAIN Switch is designated in eight gain positions from 10⁴ to 10¹¹ volts per ampere - therefore gain adjustment is straight forward. f. Variable Rise Time. Optimum response can be selected for each gain setting since a separate RISE TIME switch is provided on the front panel.