Datasheet

R
F
1.2k
R
L
500
+5VDC
D1
+5VDC
C
D
= 10 pF
+5VDC
R2
2k
C1
0.1 PF
R1
3k
LMH
6629
I
D
C
F
0.6 pF
(1.2 pF (2) series)
Vout = 3VDC - 1200 x I
D
LMH6629
www.ti.com SNOSB18G –APRIL 2010–REVISED MARCH 2013
SINGLE-SUPPLY OPERATION
The LMH6629 can be operated with single power supply as shown in Figure 62. Both the input and output are
capacitively coupled to set the DC operating point.
Figure 62. Single-Supply Operation
LOW-NOISE TRANSIMPEDANCE AMPLIFIER
Figure 63 implements a high-speed, single-supply, low-noise Transimpedance amplifier commonly used with
photo-diodes. The transimpedance gain is set by R
F
.
Figure 63. 200MHz Transimpedance Amplifier Configuration
Figure 64 shows the Noise Gain (NG) and transfer function (I-V Gain). As with most Transimpedance amplifiers,
it is required to compensate for the additional phase lag (Noise Gain zero at f
Z
) created by the total input
capacitance ( C
D
(diode capacitance) + C
CM
(LMH6629 CM input capacitance) + C
DIFF
(LMH6629 DIFF input
capacitance) ) looking into R
F
; this is accomplished by placing C
F
across R
F
to create enough phase lead (Noise
Gain pole at f
P
) to stabilize the loop.
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