AD8629 Analog Devices, AD8629 Datasheet - Page 15

• Manufacturer Part Number: AD8629
• Description: Zero Drift, Single-Supply, R/R, Input/Output Operational Amplifier
• Manufacturer: Analog Devices

Specifications of AD8629

• -3db Bandwidth: 2.5MHz
• Slew Rate: 1V/µs
• Vos: 1µV
• Ib: 30pA
• # Opamps Per Pkg: 2
• Input Noise (nv/rthz): 22nV/rtHz
• Vcc-vee: 2.7V to 6V
• Isy Per Amplifier: 1.1mA
• Packages: SOIC,SOP

PEAK-TO-PEAK NOISE
Because of the ping-pong action between auto-zeroing and
chopping, the peak-to-peak noise of the AD8628/AD8629/
AD8630 is much lower than the competition. Figure 50 and
Figure 51 show this comparison.
NOISE BEHAVIOR WITH FIRST-ORDER, LOW-PASS
FILTER
The AD8628 was simulated as a low-pass filter (see Figure 53)
and then configured as shown in Figure 52. The behavior of the
AD8628 matches the simulated data. It was verified that noise is
rolled off by first-order filtering. Figure 53 and Figure 54 show
the difference between the simulated and actual transfer functions
of the circuit shown in Figure 52.
e
BW = 0.1Hz TO 10Hz
e
BW = 0.1Hz TO 10Hz
n
n
Figure 52. First-Order Low-Pass Filter Test Circuit,
p-p = 0.5µV
p-p = 2.3µV
Figure 51. Competitor A Peak-to-Peak Noise
×101 Gain and 3 kHz Corner Frequency
Figure 50. AD8628 Peak-to-Peak Noise
IN
100kΩ
TIME (1s/DIV)
TIME (1s/DIV)
1kΩ
470pF
OUT
Rev. I | Page 15 of 24
The measured noise spectrum of the test circuit charted in
Figure 54 shows that noise between 5 kHz and 45 kHz is
successfully rolled off by the first-order filter.
TOTAL INTEGRATED INPUT-REFERRED NOISE FOR
FIRST-ORDER FILTER
For a first-order filter, the total integrated noise from the
AD8628 is lower than the noise of Competitor A.
Figure 53. Simulation Transfer Function of the Test Circuit in Figure 52
Figure 54. Actual Transfer Function of the Test Circuit in Figure 52
0.1
50
45
40
35
30
25
20
15
10
50
45
40
35
30
25
20
15
10
10
5
0
5
0
1
10
0
0
Figure 55. RMS Noise vs. 3 dB Filter Bandwidth in Hz
10
10
20
20
3dB FILTER BANDWIDTH (Hz)
30
30
100
AD8628/AD8629/AD8630
FREQUENCY (kHz)
FREQUENCY (kHz)
COMPETITOR A
40
40
50
50
AD8551
60
60
1k
70
70
80
80
AD8628
90
90
100
100
10k