AD8627/AD8626/AD8625

Rev. B | Page 14 of 20

The AD862x can safely withstand input voltages 15 V below

terminal is less than 26 V. Figure 41 through Figure 43 show the

AD862x in different configurations accommodating signals

close to the negative rail. The amplifier input stage typically

maintains picoamp-level input currents across that input

voltage range.

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+5V

20k

Ω

10k

Ω

0V

–2.5V

Figure 41. Gain of Two Inverter Response to 2.5 V Step,

Centered –1.25 V below Ground

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5V

60mV

20mV

600

Ω

0V

Figure 42. Unity Gain Follower Response to 40 mV Step,

Centered 40 mV above Ground

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+5V

20k

Ω

10k

Ω

–10mV

–30mV

0V

Figure 43. Gain of Two Inverter Response to 20 mV Step,

Centered 20 mV below Ground

The AD862x is designed for 16 nV/√Hz wideband input voltage

noise and maintains low noise performance to low frequencies,

as shown in Figure 35. This noise performance, along with the

AD862x’s low input current and current noise, means that the

AD862x contributes negligible noise for applications with large

source resistances.

The AD862x has a unique bipolar rail-to-rail output stage that

swings within 5 mV of the rail when up to 2 mA of current is

drawn. At larger loads, the drop-out voltage increases as shown

in Figure 17 and Figure 18. The AD862x’s wide bandwidth and

fast slew rate allows it to be used with faster signals than previous

single-supply JFETs. Figure 44 shows the response of AD862x,

FPBW of the part is close to 100 kHz.

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Figure 44. Unity Gain Follower Response to 20 V, 50 kHz Input Signal