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.
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-230F5 is a preamplifier with the smallest equivalent input noise voltage density among the SA series (see Figure 1).
While the input impedance of SA-230F5 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-230F5, 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.