lm611cmx National Semiconductor Corporation, lm611cmx Datasheet - Page 15

• Manufacturer Part Number: lm611cmx
• Description: Operational Amplifier And Adjustable Reference
• Manufacturer: National Semiconductor Corporation

Application Information
I = Vr/R1 = 1.24/R1
FIGURE 9. Current Source is Programmed by R1
FIGURE 11. Negative −TC Current Source
FIGURE 10. Proportional-to-Absolute-
Temperature Current Source
00922123
00922124
00922122
(Continued)
15
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 AMPLIFIER
The amp or the reference may be biased in any way with no
effect on the other, except when a substrate diode conducts
(see Guaranteed Electrical Characteristics Note 1). The amp
may have inputs outside the common-mode range, may be
operated as a comparator, or have all terminals floating with
no effect on the reference (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
The op amp, like the LM124 series, has a flexible and
relatively wide-swing output stage. There are simple rules to
optimize output swing, reduce cross-over distortion, and op-
timize capacitive drive capability:
1. Output Swing: Unloaded, the 42 µA pull-down will bring
2. Cross-over Distortion: The LM611 has lower cross-over
3. Capacitive Drive: Limited by the output pole caused by
Op Amp 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
supply nor across the inputs. These features make the in-
puts look like high impedances to input sources producing
large differential and common-mode voltages.
the output within 300 mV of V
ture range. If more than 42 µA is required, a resistor from
output to V
improved slightly if the load can be tied to V
of poorer sinking open-loop voltage gain.
distortion (a 1 V
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
transistor 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 25Ω. 200 pF may then be driven without
oscillation.
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equal to the absolute maximum supply
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