Datasheet

LM614

SNOSC21C –MAY 1998–REVISED MARCH 2013

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OPERATIONAL AMPLIFIERS

Any amp or the reference may be biased in any way with no effect on the other amps or reference, except when

a substrate diode conducts (see Electrical Characteristics). One amp input may be outside the common-mode

range, another amp may be operated as a comparator, another with all terminals floating with no effect on the

others (tying inverting input to output and non-inverting input to V

−

on unused amps is preferred). Choosing

operating points that cause oscillation, such as driving too large a capacitive load, is best avoided.

Op Amp Output Stage

These op amps, like their LM124 series, have flexible and relatively wide-swing output stages. There are simple

rules to optimize output swing, reduce cross-over distortion, and optimize capacitive drive capability:

1. Output Swing: Unloaded, the 42μA pull-down will bring the output within 300 mV of V

−

over the military

temperature range. If more than 42μA is required, a resistor from output to V

−

will help. Swing across any

load may be improved slightly if the load can be tied to V

, at the cost of poorer sinking open-loop voltage

gain

2. Cross-over Distortion: The LM614 has lower cross-over distortion (a 1 V

deadband versus 3 V

for the

LM124), and increased slew rate as shown in the characteristic curves. A resistor pull-up or pull-down will

force class-A operation with only the PNP or NPN output transistor conducting, eliminating cross-over

distortion

3. Capacitive Drive: Limited by the output pole caused by the output resistance driving capacitive loads, a pull-

down resistor conducting 1 mA or more reduces the output stage NPN r

until the output resistance is that of

the current limit 25Ω. 200pF may then be driven without oscillation.

Op Amp Input Stage

The lateral PNP input transistors, unlike most op amps, have BV

EBO

equal to the absolute maximum supply

voltage. Also, they have no diode clamps to the positive supply nor across the inputs. These features make the

inputs look like high impedances to input sources producing large differential and common-mode voltages.

Typical Applications

Figure 59. Simple Low Quiescent Drain Voltage Regulator.

Total supply current approximately 320μA, when V

= +5V.

Product Folder Links: LM614