7

LT1464/LT1465

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

±5Vsupplies.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

(1b) Typical JFET Input Op Amp

with

±5V Supplies

(1c) LT1464/LT1465 Output

with

±5V Supplies