Low-Noise Current Preamplifier SR570 — DC to 1 MHz current preamplifier SR570 Current Preamplifier 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. · 5 fA/√ Hz input noise · 1 MHz maximum bandwidth · 1 pA/V maximum gain · Adjustable bias voltage 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. · Two configurable signal filters · Variable input offset current Gain can be allocated to various stages of the amplifier to optimize the instrument’s 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 a factor of 1000. · Line or battery operation · RS-232 interface 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 Stanford Research Systems

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 unwanted DC background currents. Offset currents can be specified from ±1 pA to ±1 mA in roughly 0.1 % increments. The SR570 also has an adjustable input DC bias voltage (±5 V) that allows you to directly sink current into a virtual null (analog ground) or a selected DC bias. Toggle and Blanking Two rear-panel opto-isolated TTL inputs provide additional control of the SR570. A blanking input lets you...

High Bandwidth Mode 10-9 Current Noise (Amps/√Hz) Current Noise (Amps/√Hz) Noise vs. frequency plots High Bandwidth Mode 1 Gain / Nominal Gain (dB) Gain / Nominal Gain (dB) Gain vs. frequency plots Stanford Research Systems

Inputs Virtual null or user-set bias (±5 V) Input offset ±1 pA to ±1 mA adjustable DC offset current Maximum input ±5 mA Noise See graphs on previous page Sensitivity 1 pA/V to 1 mA/V in 1-2-5 sequence (Vernier adjustment in 0.5 % steps) Frequency response ±0.5 dB to 1 MHz (Adjustable front-panel frequency response compensation for source capacitance) Grounding Amplifier ground is fully floating. Amplifier and chassis ground are available at rear panel. Input ground can float up to ±40 V. Gain accuracy DC drift Maximum output Filters Signal filters Gain allocation Low Noise High Bandwidth Low...