LM614MN National Semiconductor, LM614MN Datasheet - Page 13

• Manufacturer Part Number: LM614MN
• Description: Quad Operational Amplifier and Adjustable Reference
• Manufacturer: National Semiconductor

Application Information
Connecting a resistor across Cathode-to-FEEDBACK cre-
ates a 0 TC current source, but a range of TCs may be
synthesized.
I = Vr/R1 = 1.24/R1
FIGURE 6. Output Voltage has Negative Temperature
FIGURE 8. Diode in Series with R1 Causes Voltage
across R1 and R2 to be Proportional to Absolute
FIGURE 9. Current Source is Programmed by R1
FIGURE 7. Output Voltage has Positive TC
Coefficient (TC) if R2 has Negative TC
if R1 has Negative TC
Temperature (PTAT)
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13
Hysteresis
The reference voltage depends, slightly, on the thermal his-
tory
vary — always check the data sheet for any given device. Do
not assume that no specification means no hysteresis.
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 sub-
strate diode conducts (see Guaranteed Electrical Character-
istics (Note 1)). 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
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 42 µA pull-down will bring
FIGURE 10. Proportional-to-Absolute-Temperature
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
of
FIGURE 11. Negative-TC Current Source
the
−
die.
will help. Swing across any load may be im-
Current Source
Competitive
−
on unused amps is preferred).
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−
over the military tempera-
micro-power
+
, at the cost of
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products