7
LT1464/LT1465
APPLICATIONS INFORMATION
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Phase Reversal Protection
Most industry standard JFET input single, dual and quad
op amps exhibit phase reversal at the output when the
negative common mode limit at the input is exceeded.
Common mode range is at a premium at ±5V supplies. The
Figures show a ±5.2V sine wave input (Figure 1a), the
response of a competing JFET input op amp in the unity-
gain follower mode (Figure 1b) and the response of the
LT1464/LT1465 (Figure 1c).
The phase reversal of Figure 1b can cause lock-up in servo
systems. The LT1464/LT1465 does not phase-reverse
when the common mode input is anywhere within the
supplies.
(1a) ±5.2V Sine Wave
LT1464 • F01a
LT1464 • F01b
LT1464 • F01c
Figure 1. Voltage Follower with Input Exceeding the Common Mode Range (V
S
= ±5V)
(1b) Typical JFET Input Op Amp
with ±5V Supplies
(1c) LT1464/LT1465 Output
with ±5V Supplies
