I am trying to generate a sort of digital signal from a random input.
For now I am using a random 1/f signal generated from Matlab with amplitude of 1 nV as input to my inverter. I have a six stage inverter with a gain of about 37 dB in each stage and at the end I am getting a random digital signal going from 0 to 1.8V.
The following table shows the bias voltage in each stage and I got my desired output.
Vout1
869m
Vout1_1
879.5m
Vout1_2
932.2m
Vout1_3
819.8m
Vout1_4
867.5m
Vout1_5
991.2m
But when I gave a different noise signal( It is still 1/f and amplitude of 1nv). The bias points have drastically changed which is understandable. Following table shows the bias voltages
Vout1
869m
Vout1_1
879.5m
Vout1_2
933.6m
Vout1_3
718.5m
Vout1_4
1.654
Vout1_5
192.8n
Is there any solution where can I force the inverter stages to be in a particular bias point through feedback? or if any better circuit I can consider to get the desired output?
For an AC or sparse pulse amplification lineup, I like "autobiased
inverters" with capacitor blocking. I have also used schemes where
a small fed-back inverter serves as a bias reference, and multiple
C-blocked stages (not fed back) receive gate bias through a high
value R (centering them "well enough" but not costing as much
signal, as the Miller-resistor-feedback-inverter.
You'd rather not have DC gain if you aren't looking for DC gain.
For noise measurement you want to determine the lower corner
frequency of interest and then see if a circuit is realizable, that
does it (like, integrating 10Mohm and 10uF ain't it, so forget a
0.01Hz noise-vs-frequency X-axis)