AD8651/AD8652

Rev. B | Page 17 of 20

1

µF

+

–

V–

3

2

U1

IN

2.7nF

33

Ω

5V

1k

Ω

10k

Ω

10k

Ω

1k

Ω

AD8651

AD7685

0V – 5V

Driving a 16-Bit ADC

The AD8651 is an excellent choice for driving high speed, high

precision ADCs. The driver amplifier for this type of

application needs to have low THD + N as well as quick settling

time. Figure 60 shows a complete single-supply data acquisition

solution. The AD8651 drives the AD7685, a 250 kSPS, 16-bit

The AD8651 is configured in an inverting gain of 1 with a 5 V

single supply. Input of 45 kHz is applied, and the ADC samples

at 250 kSPS. The results of this solution are listed in Table 6.

The advantage of this circuit is that the amplifier and ADC can

be powered with the same power supply. For the case of a

noninverting gain of 1, the input common-mode voltage

encompasses both supplies.

Figure 60. AD8651 Driving a 16-Bit ADC

Table 6. Data Acquisition Solution of Figure 60

Parameter

Reading (dB)

THD + N

105.2

SFDR

106.6

107.7

113.6

INPUT RANGE = 0 TO 5V

FREQUENCY (kHz)

0

–160

–100

–120

–140

–80

–60

–40

–20

0

10

20

30 40

50

60

70

80

90

100 110 120

http://www.analog.com/Analog_Root/productPage/productHome/0%2C21

21%2CAD7685%2C00.html

Figure 59. Frequency Response of AD8651 Driving a 16-Bit ADC