After several months of careful test we can finally present results of the analysis of the ultra-stable Multichannel Current Source performance.
The plot shows the noise spectrum of simple resistor and resistor supplied with our MSC. Although the noise itself is essentially white, the noise spectrum shows a characteristic roll-off due to the use of an output capacitor. The capacitor shapes frequency response of the system to assure stable operation with inductive loads and filter out high frequency noise. As a result for frequencies larger than 10 kHz the noise with current source connected is lower than the measurement system noise alone.
In turn, the device shows ultra-low noise (10 pA/√Hz at 1 kHz).
We have also tested the long-term stability of the source by measuring the Allan deviation. Our results showed that the system reaches its minimum at about 700 s of integration at the level of 3*10-7. We demonstrated that this drift is most likely limited by the thermal drift of reference voltage. It was demonstrated that the typical thermal drift is significantly below 5 ppm/°C.
This tests showed that our Multichannel Current Source is ready to be shipped.