LMC6484 Datasheet, PDF (33/45 Pages) National Semiconductor (TI) – CMOS Quad Rail-to-Rail Input and Output Operational Amplifier

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System Examples (continued)
LMC6484
SNOS675C – AUGUST 2000 – REVISED SEPTEMBER 2015
Figure 70. Low Voltage Peak Detector with Rail-to-Rail Peak Capture Range
In Figure 70 dielectric absorption and leakage is minimized by using a polystyrene or polyethylene hold
capacitor. The droop rate is primarily determined by the value of CH and diode leakage current. The ultra-low
input current of the LMC6484 has a negligible effect on droop.
Figure 71. Rail-to-Rail Sample and Hold
The high CMRR (85 dB) of the LMC6484 allows excellent accuracy throughout the rail-to-rail dynamic capture
range of the circuit.
R1 = R2, C1 = C2; f =
1
1
; DF =
C
2
R
2
2pR1C1
2C R
1
1
Figure 72. Rail-to-Rail Single Supply Low Pass Filter
The low pass filter circuit in Figure 72 can be used as an anti-aliasing filter with the same voltage supply as the
A/D converter. Filter designs can also take advantage of the LMC6484 ultra-low input current. The ultra-low input
current yields negligible offset error even when large value resistors are used, which allows the use of smaller
valued capacitors which take less board space and cost less.
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