LMH6611 Datasheet, PDF (27/42 Pages) Intersil Corporation – PowerWise® Single Supply 345 MHz Rail-to-Rail Output Amplifiers

LMH6611, LMH6612
www.ti.com
SNOSB00K – NOVEMBER 2007 – REVISED OCTOBER 2013
The performance of the LMH6612 with the ADC121S625 is shown in Table 2.
Table 2. Performance of the LMH6612 Combined with the ADC121S625
Amplifier
Output/ADC Input
2.5
SINAD
(dB)
68.8
SNR
(dB)
69
THD
(dB)
−81.5
SFDR
(dBc)
75.1
ENOB
11.2
Notes
ADC121S625 @ f = 20 kHz
DIFFERENTIAL TO DIFFERENTIAL ADC DRIVER
The LMH6612 dual op amp can be configured as a differential to differential ADC driver to buffer a differential
source to a differential input ADC as shown in Figure 72. The differential to differential ADC driver can be formed
using two single to single ADC drivers. Each output from these drivers goes to a separate input of the differential
ADC. Here, each single to single ADC driver uses the same components and is configured for a gain of -1
(inverting).
1 PF 549:
+IN
549:
V⁺
14.3 k:
1.24 k:
1 nF
5.6 PF
14.3 k:
0.1 PF
150 pF
V⁺
0.1 PF 10 PF
-
LMH6612
+
22:
390 pF
V⁺
0.1 PF _{10 PF}
ADC121S705
1 PF 549:
-IN
1.24 k:
549:
150 pF
22:
390 pF
V⁺
14.3 k:
1 nF
14.3 k:
5.6 PF
0.1 PF
V⁺
0.1 PF 10 PF
-
LMH6612
+
Figure 72. Differential to Differential ADC Driver
The following table summarizes the performance of the LMH6612 combined with the ADC121S625 at two
different frequencies. In order to utilize the full dynamic range of the ADC, the maximum input of 2.5 V_PP is
applied to the ADC input. Figure 73 shows the FFT plot of the LMH6612 and ADC121S625 combination tested at
f = 20 kHz input frequency.
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