AD797 datasheet(12/20 Pages) AD

12 / 20 page

AD8671/AD8672/AD8674

Data Sheet

Rev. F | Page 12 of 20

OUTPUT PHASE REVERSAL

Phase reversal is a change of polarity in the amplifier transfer

function that occurs when the input voltage exceeds the supply

voltage. The AD8671/AD8672/AD8674 do not exhibit phase

reversal even when the input voltage is 1 V beyond the supplies.

VSY = ±15V

VIN

VOUT

TIME (10

s/DIV)

Figure 31. Output Phase Reversal

TOTAL NOISE VS. SOURCE RESISTANCE

The low input voltage noise of the AD8671/AD8672/AD8674

makes them a great choice for applications with low source

resistance. However, because they have low input current noise,

they can also be used in circuits with substantial source

resistance.

Figure 32 shows the voltage noise, current noise, thermal noise,

and total rms noise of the AD8671 as a function of the source

resistance.

For RS < 475 Ω, the input voltage noise, en, dominates.

For 475 Ω < RS < 412 kΩ, thermal noise dominates.

For RS > 412 kΩ, the input current noise dominates.

100

1000

100

10k

100k

en_t

(4kRST)1/2

SOURCE RESISTANCE (

)

Figure 32. Noise vs. Source Resistance

AD797 Datasheet(PDF) 12 Page - Analog Devices