Datasheet

AD8033/AD8034
Rev. D | Page 22 of 24
02924-063 FREQUENCY (Hz)
VOLTAGE NOISE (nV/
√
Hz)
2πR
F
C
F
2πR
F
(C
F
+ C
S
+ C
M
+ 2C
D
)
(C
S
+ C
M
+ 2C
D
+ C
F
)/C
F
RF NOISE
VEN (C
F
+ C
S
+ C
M
+ 2C
D
)/C
F
f
3
f
2
f
3
=
VEN
f
1
f
2
=
f
1
=
1
1
f
CR
NOISE DUE TO AMPLIFIER
The output noise over frequency of the preamp is shown in
Figure 63.
The pole in the loop transmission translates to a zero in the
noise gain of the amplifier, leading to an amplification of the
input voltage noise over frequency. The loop transmission zero
introduced by C
F
limits the amplification. The bandwidth of the
noise gain extends past the preamp signal bandwidth and is
eventually rolled off by the decreasing loop gain of the amplifier.
Keeping the input terminal impedances matched is recommended
to eliminate common-mode noise peaking effects that add to
the output noise.
Integrating the square of the output voltage noise spectral density
over frequency and then taking the square root results in the
total rms output noise of the preamp.
Figure 63. Photodiode Voltage Noise Contributions