LMH6612MA Datasheet, PDF (24/32 Pages) Texas Instruments – Single Supply 345 MHz Rail-to-Rail Output Amplifiers

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FIGURE 5. LMH6611 and ADC121S101 Layout
SINGLE-ENDED TO DIFFERENTIAL ADC DRIVER
The single-ended to differential ADC driver in Figure 3 utilizes
an LMH6612 dual op amp to buffer a single-ended source to
drive an ADC with differential inputs. One of the op amps is
configured as a unity gain buffer that drives the inverting
(IN−) input of the op amp U2 and non-inverting (IN+) input of
the ADC121S625. U2 inverts the input signal and drives the
inverting input of the ADC121S625. The ADC driver is con-
figured for a gain of +2 to reduce the noise without sacrificing
THD performance. The common mode voltage of 2.5V is set
up at the non-inverting inputs of both op amps U1 and U2.
This configuration produces differential ±2.5 V_PP output sig-
nals, when the single-ended input signal of 0 to V_REF is AC
coupled into the non-inverting terminal of the op amp and
each non-inverting terminal of the op amp is biased at the mid-
scale of 2.5V. The two output RC anti-aliasing filters are used
between both the outputs of U1 and U2 and the input of the
ADC121S625 to minimize the effect of undesired high fre-
quency noise coming from the input source. Each RC filter
has the cutoff frequency of approximately 22 MHz.
FIGURE 6. Single-Ended to Differential ADC Driver
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