ADA4430-1

Rev. C | Page 14 of 20

USABLE INPUT VOLTAGE RANGE

The output voltage range of the ADA4430-1 limits its usable

input voltage range. The lower end of the input range is

typically 0 V. The upper end of the usable input voltage

range is calculated as

VIN (max) = (VOM − VOO)/2

where:

VIN (max) is the upper end of the usable input voltage range.

VOM is the maximum output swing.

VOO is the output-referred offset voltage.

SAG CORRECTION FREQUENCY RESPONSE

When using the SAG corrected circuit, the gain from the input

to the immediate output of the ADA4430-1 is ×2.5 (

≈8 dB) at

extremely low frequencies where the outer feedback loop

formed by the 22 μF capacitor effectively opens (see Figure 29)

and exhibits a second-order peak of approximately 11 dB at

about 5 Hz. This gain is approximately 7.5 dB at 30 Hz. The

extra gain must be accounted for when considering low

frequency input and output signal swings to keep them within

their specified limits. The gain from the ADA4430-1 input to

the load side of the 47 μF capacitor does not exhibit this

behavior; rather, it appears more like a single-pole high-

pass response. Figure 32 illustrates the SAG frequency response

immediately at the ADA4430-1 output and at the load side of the

47 μF capacitor.

12

10

8

6

4

2

0

–2

–4

–6

–8

–10

1

10

100

1000

100000

10000

FREQUENCY (Hz)

AT ADA4430-1 OUTPUT

AT LOAD SIDE OF 47µF CAPACITOR

Figure 32. SAG Corrected Frequency Response at ADA4430-1 Output and

at the Load Side of the 47 μF Capacitor