The SR570 is a low-noise current preamplifier capable of current gains as large as 1 pA/V. High gain and bandwidth, low noise, and many convenient features make the SR570 ideal for a variety of photonic, low temperature and other measurements.
Gain
The SR570 has sensitivity settings from 1 pA/V to 1 mA/V that can be selected in a 1-2-5 sequence. A vernier gain adjustment is also provided that lets you select any sensitivity in between.
Gain can be allocated to various stages of the amplifier to optimize the instruments performance. The low noise mode places gain in the front end of the amplifier for the best noise performance. The high bandwidth mode allocates gain to the later stages of the amplifier to improve the frequency response of the front end. In the low drift mode, the input amplifier is replaced with a very low input-current op amp, reducing the instrument's DC drift by up to a factor 1000.
Block Diagram
Filters
The SR570 contains two first-order RC filters whose cutoff frequency and type can be configured from the front panel. Together, the filters can be configured as a 6 or 12 dB/oct rolloff low-pass or high-pass filter, or as a 6 dB/oct rolloff band-pass filter. Cutoff frequencies are adjustable from 0.03 Hz to 1 MHz in a 1-3-10 sequence. A filter reset button is included to shorten the overload recovery time of the instrument when long filter time constants are used.
Input Offset and DC Bias
An input offset-current adjustment is provided to suppress any undesired DC background currents. Offset currents can be specified from ±1 pA to ±1 mA in roughly 0.1 % increments