AD8674_15 Datasheet, PDF (12/20 Pages) Analog Devices – Precision, Very Low Noise, Low Input

AD8671/AD8672/AD8674
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.
V_SY = ±15V
V_IN
V_OUT
TIME (10s/DIV)
Figure 31. Output Phase Reversal
Data Sheet
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.
1000
100
10
1
10
C
i_n
e_{n_t}
(4kR_ST)^1/2
e_n
A
B
100
1k
10k
100k
1M
SOURCE RESISTANCE ()
Figure 32. Noise vs. Source Resistance
Rev. F | Page 12 of 20