Driving the future of technology : Original solution in measurement and control

 Lecture for Measurement

Posted 2019/7/19

Voltage amplifier ("voltage to voltage amplifier")

NF voltage amplifier

Although we sell power amplifiers like the HSA series and BP series, here we introduce preamplifiers called “SA series” used for amplifying micro-voltage signals.

1. Extremely low-noise characteristics

One of the key performance requirements for preamplifiers is low noise. Since an amplifier itself always superimposes some noise, in order to get more accurate measurement, it is preferable to use the amplifiers with lower noise.

One of the performance indicators of such a preamplifier is equivalent input noise. It can be expected that as the noise value decreases, the signal amplification becomes better with less noise superposition.

We offer multiple preamplifiers, among which the SA series is specialized for low noise. In that series, SA-250F6 is a preamplifier with the smallest equivalent input noise voltage density among the SA series (see Figure 1).


While the input impedance of SA-250F6 is 50 Ω, an equivalent input noise voltage density of 0.25 nV/√Hz (typ.) (which is lower than the thermal noise (0.91 nV/√Hz) due to a 50 Ω resistance at room temperature) is achieved because of its unique circuit technology. Note that the thermal noise due to the 50 Ω resistance can be reduced by lowering the temperature; however, to make it as small as equivalent input noise voltage density of SA-250F6, it is necessary to reduce the temperature to 22.5 K (about -251°C). That temperature is in the cryogenic realm and slightly higher than liquid-hydrogen temperature (about 21 K, see Figure 2). From this fact, it can be understood that such low noise level cannot be achieved with normally designed amplifier.


Related Product

Extremely low noise amplifier SA Series

Extremely low noise, excellent stability, wideband preamplifier for detection of extremely small signals

     Low noise
  • Adopted our exclusive circuit applying negative feedback technology
    SA-250F6: at input impedance of 50 Ω, noise figure of 0.6 dB and equivalent input noise voltage density of 0.25 nV/√Hz
  •  Wideband
  • A wide frequency band from low-frequency signals including DC (SA-200F3/240F5/410F3/440F5) to high-frequency, high-speed signals (SA-250F6/251F6) exceeding 100 MHz is covered.
  •  Input mode according to signal source
  • Single-ended (single-wire-grounded) input, single-ended FET input, differential input, and differential FET input



Related keywords :  Ultra low noise amplifier, LNA

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