ADA4622-1ARJZ-R2 datasheet(31/36 Pages) AD

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Data Sheet

ADA4622-1/ADA4622-2/ADA4622-4

APPLICATIONS INFORMATION

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Rev. F | 31 of 36

p-p. The amplifiers have a bandwidth of 2 MHz when they are

maximized for a 45° phase margin with CF = 2 pF. Note that with

the PCB parasitics added to CF, the peaking is only 0.5 dB, and the

bandwidth is reduced slightly.

Increasing CF to 3 pF completely eliminates the peaking; however,

increasing CF to 3 pF reduces the bandwidth to 1 MHz.

Table 13 shows the noise sources and total output noise for the

photodiode preamp, where the preamp is configured to have a 45°

phase margin for maximum bandwidth and fZ = fX = fN in this case.

Figure 97. Transimpedance Photodiode Preamplifier

Figure 98. Transimpedance Photodiode Preamplifier Frequency Response

Table 13. RMS Noise Contributions of the Photodiode Preamplifier

Contributor

Expression

RMS Noise (µV)1

4kT×RF×fN× π2

50.8

VNOISE

VNOISE× (CS+CM+CF+CD)

CF × π2×fN

131.6

Root Sum Square (RSS) Total

RF2×VNOISE2

141

1 RMS noise with RF = 50 kΩ, CS = 5 pF, CF = 2 pF, CM = 3.7 pF, and CD = 0.4 pF.

ADA4622-1ARJZ-R2 Datasheet(PDF) 31 Page - Analog Devices