LM613AIN National Semiconductor, LM613AIN Datasheet - Page 17

• Manufacturer Part Number: LM613AIN
• Description: Dual Operational Amplifiers/ Dual Comparators/ and Adjustable Reference
• Manufacturer: National Semiconductor

Application Information
Reference Hysteresis
The reference voltage depends, slightly, on the thermal his-
tory of the die. Competitive micro-power products vary — al-
ways check the data sheet for any given device. Do not as-
sume that no specification means no hysteresis.
OPERATIONAL AMPLIFIERS AND COMPARATORS
Any amp, comparator, or the reference may be biased in any
way with no effect on the other sections of the LM613, ex-
cept when a substrate diode conducts, see Electrical Char-
acteristics (Note 1). For example, one amp input may be out-
side the common-mode range, another amp may be
operating as a comparator, and all other sections may have
all terminals floating with no effect on the others. Tying in-
verting input to output and non-inverting input to V
used amps is preferred. Unused comparators should have
non-inverting input and output tied to V
tied to V
such as driving too large a capacitive load, is best avoided.
Op Amp Output Stage
These op amps, like the 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 42 µA pull-down will bring
2. Cross-Over Distortion: The LM613 has lower cross-over
Typical Applications
the output within 300 mV of V
ture range. If more than 42 µA is required, a resistor from
output to V
proved slightly if the load can be tied to V
poorer sinking open-loop voltage gain.
distortion (a 1 V
−
. Choosing operating points that cause oscillation,
−
will help. Swing across any load may be im-
BE
deadband versus 3 V
−
over the military tempera-
FIGURE 12. High Current, High Voltage Switch
+
, and inverting input
(Continued)
+
, at the cost of
BE
−
for the
on un-
17
3. Capacitive Drive: Limited by the output pole caused by
Comparator Output Stage
The comparators, like the LM139 series, have open-collector
output stages. A pull-up resistor must be added from each
output pin to a positive voltage for the output transistor to
switch properly. When the output transistor is OFF, the out-
put voltage will be this external positive voltage.
For the output voltage to be under the TTL-low voltage
threshold when the output transistor is ON, the output cur-
rent must be less than 8 mA (over temperature). This im-
pacts the minimum value of pull-up resistor.
The offset voltage may increase when the output voltage is
low and the output current is less than 30 µA. Thus, for best
accuracy, the pull-up resistor value should be low enough to
allow the output transistor to sink more than 30 µA.
Op Amp and Comparator Input Stage
The lateral PNP input transistors, unlike those of most op
amps, have BV
voltage. Also, they have no diode clamps to the positive sup-
ply nor across the inputs. These features make the inputs
look like high impedances to input sources producing large
differential and common-mode voltages.
LM124), and increased slew rate as shown in the char-
acteristic curves. A resistor pull-up or pull-down will force
class-A operation with only the PNP or NPN output tran-
sistor conducting, eliminating cross-over distortion.
the output resistance driving capacitive loads, a
pull-down resistor conducting 1 mA or more reduces the
output stage NPN r
the current limit 25 . 200 pF may then be driven without
oscillation.
DS009226-40
EBO
equal to the absolute maximum supply
e
until the output resistance is that of
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