AD8627/AD8626/AD8625

Rev. B | Page 13 of 20

APPLICATIONS

The AD862x is one of the smallest and most economical

JFETs offered. It has true single-supply capability and has

an input voltage range that extends below the negative rail,

allowing the part to accommodate input signals below ground.

The rail-to-rail output of the AD862x provides the maximum

dynamic range in many applications. To provide a low offset,

low noise, high impedance input stage, the AD862x uses

n-channel JFETs The input common-mode voltage extends

amplifier, configured in unity gain buffer, closer than 2 V to the

positive rail causes an increase in common-mode voltage error,

as illustrated in Figure 15, and a loss of amplifier bandwidth.

This loss of bandwidth causes the rounding of the output

waveforms shown in Figure 39 and Figure 40, which have inputs

The AD862x will not experience phase reversal with input

signals close to the positive rail, as shown in Figure 29. For input

noninverting input prevents phase reversal at the expense of

greater input voltage noise. This current limiting resistor should

also be used if there is a possibility of the input voltage

exceeding the positive supply by more than 300 mV, or if an

these conditions will damage the amplifier if the condition

exists for more than 10 seconds. A 100 kΩ resistor allows the

amplifier to withstand up to 10 V of continuous overvoltage,

while increasing the input voltage noise by a negligible amount.

TIME (2

INPUT

OUTPUT

Figure 39. Unity Gain Follower Response to 0 V to 4 V Step

TIME (2

INPUT

OUTPUT

Figure 40. Unity Gain Follower Response to 0 V to 5 V Step