LMH6618MK NSC [National Semiconductor], LMH6618MK Datasheet - Page 23

• Manufacturer Part Number: LMH6618MK
• Description: 130 MHz, 1.25 mA Rail-to-Rail Input and Output Operational Amplifier with Shutdown
• Manufacturer: NSC [National Semiconductor]

Note:
GBWP = 65 MHz
C
C
V
Figure 11 shows the frequency response for the various pho-
todiodes in Table 2.
FIGURE 11. Frequency Response for Various Photodiode
S
T
IN
= C
= ±2.5V
= 2 pF
PD
(pF)
C
100
222
22
47
+ C
PD
IN
and Feedback Capacitors
(pF)
102
224
C
24
49
T
TABLE 2. TIA (Figure 1) Compensation and Performance Results
C
10.9
15.8
23.4
(pF)
F CAL
7.7
20195868
C
F USED
(pF)
5.6
10
15
18
23
When analyzing the noise at the output of the TIA, it is im-
portant to note that the various noise sources (i.e. op amp
noise voltage, feedback resistor thermal noise, input noise
current, photodiode noise current) do not all operate over the
same frequency band. Therefore, when the noise at the out-
put is calculated, this should be taken into account. The op
amp noise voltage will be gained up in the region between the
noise gain’s zero and pole (f
the values of R
starts and therefore its contribution to the total output noise
will be larger. It is obvious to note that it is advantageous to
minimize C
reverse bias across the diode at the expense of excess dark
current and noise.
f
−3 dB CAL
(MHz)
IN
23.7
16.6
11.5
7.81
by proper choice of op amp or by applying a
F
and C
T
, the sooner the noise gain peaking
f
Z
−3 dB MEAS
and f
(MHz)
15.2
10.8
20
8
P
in Figure 10). The higher
Peaking
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(dB)
0.9
0.8
0.9
2.9