LMC6582AIMX NSC [National Semiconductor], LMC6582AIMX Datasheet - Page 15

• Manufacturer Part Number: LMC6582AIMX
• Description: Low Voltage, Rail-To-Rail Input and Output CMOS Operational Amplifier
• Manufacturer: NSC [National Semiconductor]

Oscillators
and
Then,
LMC6582/4 as a Comparator
Figure 20 shows the application of the LMC6582/4 as a com-
parator. The hysteresis is determined by the ratio of the two
resistors. Since the supply current of the LMC6582/4 is less
than 1 mA per amplifier, it can be used as a low power com-
parator, in applications where the quiescent current is an im-
portant parameter.
Typical propagation delays
of t
Filters
The filter shown in Figure 21 is used to process “voice-band”
signals. The bandpass filter has a flatband gain of 40 dB.
The two corner frequencies, f
z
t
2
1 Hz
t
PHL
1
= 0.74 seconds
= 0.27 seconds
= 6 µs, and t
FIGURE 21. Wide-Band Band-Pass Filter
FIGURE 20. Comparator with Hysteresis
(Continued)
PLH
= 5 µs.
@
V
1
S
and f
= 3V would be on the order
2
, are calculated as:
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The LMC6582/4, with its rail-to-rail input common mode volt-
age range and high gain (120 dB typical, R
tremely well suited for such filter applications. The rail-to-rail
input range allows for large input signals to be processed
without distortion. The high gain means that the circuit can
provide filtering and gain in one stage, instead of the typical
two stage filter. This implies a reduction in cost, and a sav-
ings of space and power.
This is an illustration of a conceptual use of the LMC6582/4.
The selectivity of the filter can be improved by increasing the
order (number of poles) of the design.
Sample-and-Hold Circuits
When the “switch” is closed during the sample interval,
C
“switch” is open, C
the high input impedance of the LMC6582/4.
Errors in the “hold” voltage are caused by the input current of
the amplifier, the leakage current of the CD4066, and the
leakage current of the capacitor. While an input current of 80
fA minimizes the accumulation rate for error in the circuit, the
LMC6582/4’s CMRR of 82 dB allows excellent accuracy
throughout the amplifier’s rail-to-rail dynamic capture range.
Battery Monitoring Circuit
HOLD
FIGURE 23. Circuit Used to Sense Charging.
charges up to the value of the input signal. When the
FIGURE 22. Sample-and-Hold Application
HOLD
retains this value as it is buffered by
L
= 10 k ) is ex-
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