→ t

and

→t

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.

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

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

DS012041-28

FIGURE 20. Comparator with Hysteresis

DS012041-29

FIGURE 21. Wide-Band Band-Pass Filter

DS012041-31

FIGURE 22. Sample-and-Hold Application

DS012041-33

FIGURE 23. Circuit Used to Sense Charging.

www.national.com

15