AD8033AKSZ-R2 datasheet(23/25 Pages) AD

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AD8033/AD8034

Rev. D | Page 22 of 24

FREQUENCY (Hz)

2πRF CF

2πRF (CF + CS + CM + 2CD)

(CS + CM + 2CD + CF)/CF

RF NOISE

VEN (CF + CS + CM + 2CD)/CF

f3 =

VEN

f2 =

f1 =

fCR

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 CF 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

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