NF Corporation: Low-noise preamplifier selection guide

Differential input type

Reliably amplify a wide range of voltage signals between sub-µV and several mV
Lineup of models supporting a wide frequency range between DC and up to 500MHz
The most suitable model can be selected according to the signal source resistance.

	Input type	Gain	Bandwidth	Input resistance	Noise voltage density	Noise current density	Noise figure
SA-410F3	Differential input	40dB	DC to 1MHz	1kΩ/ 10kΩ/ 100kΩ	0.75nV/√Hz	4.5pA/√Hz	-
SA-420F5		46dB	1kHz to 80MHz	1MΩ	0.9nV/√Hz	100fA/√Hz	-
SA-421F5		46dB	30Hz to 30MHz	1MΩ	0.5nV/√Hz	100fA/√Hz	-
SA-430F5		46dB	1kHz to 100MHz	50Ω	0.35nV/√Hz	7pA/√Hz	1.0dB
SA-440F5		40dB	DC to 20MHz	1MΩ/ 100MΩ/ OPEN	1.8nV/√Hz	25fA/√Hz	-

The model line-up supports a wide voltage input range. Includes extremely small voltages of less than 1 μV.

Supports models with frequency ranges up to 100MHz. Achieves low noise specifications compared to competitors.

An amplifier suitable for the signal source resistance of the sensor can be selected. Achieves low-noise signal output.

Output waveform comparison at 100μVp-p square wave input

SA-410F3 (DC to 1MHz, 0.75nV/√Hz)

SA-420F5 (1kHz to 70MHz, 0.9nV/√Hz)

SA-421F5 (30Hz to 30MHz, 0.5nV/√Hz)

SA-430F5 (1kHz to 100MHz, 0.35nV/√Hz)

SA-440F5 (DC to 20MHz, 1.8nV/√Hz)

Small signals amplified by the SA series are observed with an oscilloscope.

SA-410F3

Input signal: 5μVp-p, sine wave
Oscilloscope: 1MHz bandwidth
LPF: Connected after the amplifier and set a cutoff frequency about 5 times the signal frequency*

Detects 5µVp-p real-time signals

Waveform without LPF

*Using an appropriate LPF can reduce overall noise as shown above.

Connect multiple SA series units and observe using the averaging function of the oscilloscope.

Measurement block diagram

Measurement results

SA-410F3

4nVp-p signal detected