Low Noise Pre-Amplifier

Today i have finished to complete the low noise pre-amplifier. In the following text i repor some measure on this pre-amplifier:

The Gain is around 100.

Noise (input 50 ohm):



The noise in input is around 1 nV.

Noise (input short circuit):




The Noise is around 0.8 nV

Transfer Function

1) as usual measurements corresponding to different configurations must be presented in the same plot, to allow direct comparison of the results, for example graphs (1 and 2) or (2 and 4).
2) I would increase the resolution at low frequency, I would let the window go from 10Hz to 1.6kHz

Please update the graphs and give an estimate of the pre-amp noise referred to the input.

P.S.: "corto circuito" is "short circuit"

Range 10 - 1.6 khz:





With input signal of 1 Khz.

Maurizio,
you should plot the noise referred to the input of the pre-amp, so we can make a direct coparison with the LIGO pre-amp assembly that I report here for simplicity. It seems that their noise floor is about 0.8nV/Hz^1/2 @ 1kHz.

It seems that the noise is around 1 nV @ 1kH, but on low frequency is noisly.

Even if we understand that the new low noise pre-amplifier is showing a moise level higher than expected, I measured the dark noise of the PD12595 in two conditions: with its own VIGO pre-amp and with the new pre-amp by Maurizio.
The result is shown below in terms of NEP.



As it can be seen from the graph, the dark noise of the PD is about a factor of two higher with the new pre-amp than with the VIGO pre-amp. Moreover, in the spectrum with the new pre-amp, there are a huge number of peaks, more than expected if they were due to the 50Hz.

I also found out that the Maurizio pre-amp is giving a high DC output, approx 1.7Vdc, no matter if the input is open, shorted or closed on 50ohm.