LMH6624_16 Datasheet, PDF (23/38 Pages) Texas Instruments – LMH6624 and LMH6626 Single/Dual Ultra Low Noise Wideband Operational Amplifier

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8 Application and Implementation
LMH6624, LMH6626
SNOSA42G – NOVEMBER 2002 – REVISED DECEMBER 2014
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
A Transimpedance amplifier is used to convert the small output current of a photodiode to a voltage, while
maintaining a near constant voltage across the photodiode to minimize non-linearity. Extracting the small signal
requires high gain and a low noise amplifier, and therefore, the LMH6624 and LMH6626 devices are ideal for
such an application in order to maximize SNR. Furthermore, because of the large gain (R_F value) needed, the
device used must be high speed so that even with high noise gain (due to the interaction of the feedback resistor
and photodiode capacitance), bandwidth is not heavily impacted.
Figure 47 implements a high-speed, single supply, low-noise Transimpedance amplifier commonly used with
photo-diodes. The transimpedance gain is set by R_F.
8.2 Typical Application
5 VDC
CF
1.1 pF
D1
CD = 10 pF
ID
R2
2k
5 VDC
RF
1.2 kΩ
5 VDC
–
LMH6624
+
RL
500 Ω
C1
R1
0.1 µF
3k
VOUT = 3 VDC - 1200 × I D
Figure 57. LMH6624 Application Schematic
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