(a) VI(PP) = −1.5 V TO4.5 V

(b) OUTPUT PHASE REVERSAL

EXHIBITED BY LM358

(c) NO PHASE REVERSAL

EXHIBITED BY LT1013

−1

0

1

2

3

4

5

−1

0

1

2

3

4

5

−1

0

1

2

3

4

5

−2

18

LT1013, LT1013D, LT1013M, LT1013AM

SLOS018I – MAY 1988 – REVISED JULY 2016

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Copyright © 1988–2016, Texas Instruments Incorporated

Feature Description (continued)

7.3.3 Low-Supply Operation

The minimum supply voltage for proper operation of the LT1013x is 3.4 V (three NiCad batteries). Typical supply

current at this voltage is 290 µA; therefore, power dissipation is only 1 mW per amplifier.

7.3.4 Output Phase Reversal Protection

includes ground, and the output swings to within a few millivolts of ground.

Furthermore, the LT1013x has specific circuitry that addresses the difficulties of single-supply operation, both at

the input and at the output. At the input, the driving signal can fall below 0 V, either inadvertently or on a

transient basis. If the input is more than a few hundred millivolts below ground, the LT1013x is designed to deal

with the following two problems that can occur:

1. On many other operational amplifiers, when the input is more than a diode drop below ground, unlimited

current flows from the substrate (VCC

− terminal) to the input, which can destroy the unit. On the LT1013x,

the 400-Ω resistors in series with the input protect the device, even when the input is 5 V below ground.

amplifiers saturates, and phase reversal occurs at the output. This can cause lockup in servo systems.

Because of unique phase-reversal protection circuitry (Q21, Q22, Q27, and Q28), the LT1013x outputs do

not reverse, even when the inputs are at

−1.5 V (see Figure 24).

This phase-reversal protection circuitry does not function when the other operational amplifier on the LT1013x is

driven hard into negative saturation at the output. Phase-reversal protection does not work on amplifier 1 when

amplifier 2 output is in negative saturation nor on amplifier 2 when amplifier 1 output is in negative saturation.

At the output, other single-supply designs either cannot swing to within 600 mV of ground or cannot sink more

than a few micro amperes while swinging to ground. The all-npn output stage of the LT1013x maintains its low

output resistance and high-gain characteristics until the output is saturated. In dual-supply operations, the output

stage is free of crossover distortion.

Figure 24. Voltage-Follower Response With Input Exceeding the Negative Common-Mode Input Voltage

Range