5
of
10
1
10
100
1000
10000
10
100
1000
10000
100000
1000000
Current
noise
density
(fA/
Hz)
Frequency
(Hz)
1
10
100
1000
10000
10
100
1000
10000
100000
1000000
Current
noise
density
(fA/
Hz)
Frequency
(Hz)
Cs
=
1.2nF
Cs
is
the
input shunt
capacitance
Cs
is
the
input shunt
capacitance
Cs
=
120pF
Cs
=
12nF
Cs
=
1.2nF
Figure
3:
SR555
input
current
noise
density
Figure
4:
SR556
input
current
noise
density
