OP292_15 Datasheet, PDF (13/20 Pages) Analog Devices – Dual/Quad Single-Supply Operational Amplifiers

APPLICATIONS INFORMATION
PHASE REVERSAL
The OP492 has built-in protection against phase reversal when
the input voltage goes to either supply rail. In fact, it is safe for
the input to exceed either supply rail by up to 0.6 V with no risk
of phase reversal. However, the input should not go beyond the
positive supply rail by more than 0.9 V; otherwise, the output
will reverse phase. If this condition occurs, the problem can be
fixed by adding a 5 kΩ current limiting resistor in series with
the input pin. With this addition, the input can go to more than
5 V beyond the positive rail without phase reversal.
An input voltage that is as much as 5 V below the negative rail
will not result in phase reversal.
1V
100
90
5V
0V
11.8V p-p ^OP492
2kΩ
10
0%
5µs
Figure 34. Output Phase Reverse If Input Exceeds
the Positive Supply (V+) by More Than 0.9 V
OP292/OP492
5V
0V
10V p-p ^OP492
1V/DIV
2kΩ
4ms/DIV
Figure 35. No Negative Rail Phase Reversal, Even with Input Signal
at 5 V Below Ground
POWER SUPPLY CONSIDERATIONS
The OP292/OP492 are designed to operate equally well at single
+5 V or ±15 V supplies. The lowest supply voltage recommended
is 4.5 V.
It is a good design practice to bypass the supply pins with a
0.1 μF ceramic capacitor. It helps improve filtering of high
frequency noise.
For dual-supply operation, the negative supply (V−) must be
applied at the same time, or before V+. If V+ is applied before V−,
or in the case of a loss of the V− supply, while either input is
connected to ground or another low impedance source, excessive
input current may result. Potentially damaging levels of input
current can destroy the amplifier. If this condition can exist,
simply add a l kΩ or larger resistor in series with the input to
eliminate the problem.
Rev. C | Page 13 of 20