6

LT1457

Small-Signal Response

LT1457 TPC20

LT1457 TPC19

LT1457 TPC21

Large-Signal Response

Small-Signal Response

Phase Reversal Protection

Most industry standard JFET input single, dual, and quad

op amps (e.g., LF156, LF351, LF353, LF411, LF412,

OP-15, OP-16, OP-215, and TL084) exhibit phase reversal

at the output when the negative common-mode limit at the

input is exceeded (i.e., below –12V with

±15V supplies).

The photos show a

±16V sine wave input (A), the response

of an LF412A in the unity gain follower mode (B), and the

response of the LT1457 (C).

The phase reversal of photo (B) can cause lock-up in servo

systems. The LT1457 does not phase-reverse due to a

unique phase reversal protection circuit.

All Photos 5V/Div Vertical Scale, 50

µs/Div Horizontal Scale

(B) LF412A Output

(A)

±16V Sine Wave Input

(C) LT1457 Output

LT1457 AI03

LT1457 AI01

LT1457 AI02