Tested In Full Working Condutions Stanford Research Systems SR570
Amplifiers
Description of Stanford Research Systems SR570 Amplifiers
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.
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. 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 quickly turn off/on the
instrument's gain which is useful in preventing front-end overloading. A toggle input inverts the sign of the gain in response to a TTL
signal allowing you to perform synchronous detection with a chopped
signal.
Battery Operation
Three rechargeable lead-acid batteries provide up to 15 hours of battery-powered operation. An internal battery charger automatically charges the batteries
when the unit is connected to the line. The charger senses the
battery state and adjusts the charging rate accordingly. Two rear-panel LEDs indicate the charge state of the batteries. When the batteries
become discharged they are automatically disconnected from the
amplifier circuit to avoid battery damage.
No Digital Noise
The microprocessor that runs the SR570 is "asleep" except during
the brief interval it takes to change the instrument's setup. This
ensures that no digital noise will contaminate low-level analog
signals.
| SR570 Specifications |
| Input |
| 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 table below |
| Sensitivity | 1 pA/V to 1 mA/V in 1-2-5 sequence (vernier adj. 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. |
| Filters |
| Signal filters | 2 configurable (low-pass or high-pass) 6 dB/oct rolloff filters. -3
dB points are settable in a 1-3-10 sequence from 0.03 Hz to 1 MHz. |
| Gain allocation |
| Low noise | Gain is allocated to the front end for best noise performance. |
| High bandwidth | Front-end gain is reduced for optimum frequency response. |
| Low drift | Low bias current amplifier is used for reduced drift at high
sensitivity. |
| Filter reset | Long time constant filters may be reset with front-panel button. |
| Output |
| Gain accuracy | ±0.5 % of output + 10 mV
(25 °C) |
| DC drift | See table below |
| Maximum output | ±5 V into a high impedance load |
| General |
| External blanking | TTL input sets gain to zero |
| External toggle | TTL input inverts gain polarity |
| Rear panel biasing | ±12 VDC @ 200 mA, referenced to amplifier ground |
| Computer interface | RS-232, 9600 baud, receive only |
| Power | 100/120/220/240 VAC, 6 watts charged, 30 watts while charging.
Internal batteries provide 15 hours of operation between charges.
Batteries are charged while connected to the line. |
| Dimensions | 8.3" × 3.5" × 13.0" (WHL) |
| Weight | 15 lbs. (batteries installed) |
| Warranty | One year parts and labor on defects in materials and workmanship |
| | | |
Sensitivity
(A/V) | Bandwidth
(-3 dB)* | Noise/vHz** | Temp. coefficient ± (%input + offset)/°C | DC Input
Impedance |
| High BW | Low Noise | High BW | Low Noise | Low Drift (11 to 28 °C) | All Modes |
| 10-3 | 1.0 MHz | 1.0 MHz | 150 pA | 150 pA | 0.01 % + 20 nA | 1 Ω |
| 10-4 | 1.0 MHz | 500 kHz | 100 pA | 60 pA | 0.01 % + 2 nA | 1 Ω |
| 10-5 | 800 kHz | 200 kHz | 60 pA | 2 pA | 0.01 % + 200 pA | 100 Ω |
| 10-6 | 200 kHz | 20 kHz | 2 pA | 600 fA | 0.01 % + 20 pA | 100 Ω |
| 10-7 | 20 kHz | 2 kHz | 600 fA | 100 fA | 0.01 % + 2 pA | 10 kΩ |
| 10-8 | 2 kHz | 200 Hz | 100 fA | 60 fA | 0.01 % + 400 fA | 10 kΩ |
| 10-9 | 200 Hz | 15 Hz | 60 fA | 10 fA | 0.025 % + 40 fA | 1 MΩ |
| 10-10 | 100 Hz | 10 Hz | 10 fA | 5 fA | 0.025 % + 20 fA | 1 MΩ |
| 10-11 | 20 Hz | 10 Hz | 10 fA | 5 fA | 0.040 % + 20 fA | 1 MΩ |
| 10-12 | 10 Hz | 10 Hz | 5 fA | 5 fA | 0.040 % + 20 fA | 1 MΩ |
* Frequency Compensation adjusted for flat frequency response
** Average noise in the frequency range below the 3 dB point but
above the frequency where 1/f noise is significant |
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