Low Noise | Low Drift Differential Amplifier

SP1004

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The low-noise low-drift (LNLD) differential amplifier combines ultra-low input voltage noise and excellent stability (low offset voltage drift). This 1 MHz bandwidth true-differential voltage amplifier offers unique features such as a floating input and actively stabilized offset voltage drift. Low input voltage noise is reached using a discrete dual J-FET (IF 3602) input stage. We carefully screen and select only the best, lowest noise input transistors.

The units are small and light (290 grams) and can easily be mounted close to the experiment, e.g., directly on the breakout box or the cryostat. This versatile laboratory voltage preamplifier offers three decades of gain, from 100 up to 10000, and an integrated low-pass filter with a cut-off between 100 Hz and 1 MHz. A remote control unit is available to adjust gain and filter settings remotely. AC or DC coupling is possible, and the input resistance can be switched between 10 MΩ, 1 GΩ,, and infinite (DC only). The device tolerates a common-mode voltage of up to ±1 V.

The offset voltage drift of the low noise J-FET input stage is reduced by a precise servo control-loop to below 0.3 μV/K. This unique feature is only offered by our preamplifiers. In other commercial instruments, the input voltages may drift by many 10s of μVs over time. In experiments where the voltage applied to the device is relevant to the μV level, the stabilized input voltage bias is very valuable. 

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The differential amplifier output ground is isolated from the power supply and the computer interface. Hence, the cables coming from the experiment provide the measurement ground. This grounding scheme helps avoid ground loops without a need for batteries and enables an ultra-low noise setup.