3 – 6
Performance Details
Table 3.3: Maximum input signals before PSD overload
Sensitivity
Maximum
High Res.
Normal
Low Noise
input (RMS)
100 nV
7
µ
V
200 nV
24
µ
V
500 nV
63
µ
V
100 nV
1
µ
V
7
µ
V
200 nV
2
µ
V
24
µ
V
500 nV
5
µ
V
63
µ
V
100 nV
1
µ
V
10
µ
V
130
µ
V
200 nV
2
µ
V
20
µ
V
250
µ
V
500 nV
5
µ
V
50
µ
V
650
µ
V
1
µ
V
10
µ
V
100
µ
V
1.3 mV
2
µ
V
20
µ
V
200
µ
V
2.5 mV
5
µ
V
50
µ
V
500
µ
V
6.5 mV
10
µ
V
100
µ
V
1 mV
12.5 mV
20
µ
V
200
µ
V
2 mV
14 mV
50
µ
V
500
µ
V
5 mV
14 mV
100
µ
V
1 mV
10 mV
129 mV
200
µ
V
2 mV
20 mV
160 mV
500
µ
V
5 mV
50 mV
160 mV
1 mV
10 mV
100 mV
1.25 V
2 mV
20 mV
200 mV
1.25 V
5 mV
50 mV
500 mV
1.25 V
10 mV
100 mV
1.25 V
20 mV
200 mV
1.25 V
50 mV
500 mV
1.25 V
100 mV
1.25 V
200 mV
1.25 V
500 mV
1.25 V
3.3
Input filter details
The input filter is constructed as a state-variable filter with user-
settable cuto
ff
frequency
f
0
and Q-factor. In the SR124, the peak
gain of the input filter is calibrated to be unity. The nominal transfer
functions are shown in the following figures.
Of particular note is that the pass-band portion of the low pass and
high pass filters have a gain of 1
/
Q far from the resonance. For
most applications requiring low pass or high pass input filtering, it
is e
ff
ective to leave Q
=
1.
SR124
Analog Lock-In Amplifier
