lmc6582 National Semiconductor Corporation, lmc6582 Datasheet - Page 11

• Manufacturer Part Number: lmc6582
• Description: Low Voltage, Rail-to-rail Input And Output Cmos Operational Amplifier
• Manufacturer: National Semiconductor Corporation

3.0 Low Voltage Operation
At V
common-mode voltage range. Figure 4 shows an input volt-
age extending to both supplies and the resulting output.
The amplifier is operational at V
put common-mode voltage range, output swing, and CMRR
specs. Figure 5 shows the response of the LMC6582/4 at V
Figure 6 shows an input voltage exceeding both supplies
with no resulting phase inversion on the output.
= 1.8V.
NiMH
NiCd
Lead-Acid
Silver Oxide
Carbon-Zinc
Lithium
Battery Type
S
Range Extends to Both Supplies at V
FIGURE 4. The Input Common-Mode Voltage
= 2.2V, the LMC6582/4 has a rail-to-rail input
FIGURE 5. Response of the LMC6582/4
Nominal Voltage
2.6V–3.6V
at V
1.2V
1.2V
1.6V
1.5V
2V
S
= 1.8V
S
= 1.8V, with guaranteed in-
End of Discharge
1.7V–2.4V
Voltage
S
(Continued)
1.8V
1.3V
1.1V
1V
1V
= 2.2V
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4.0 Capacitive Load Tolerance
The LMC6582/4 can typically drive a 100 pF load with V
10V at unity gain without oscillating. The unity gain follower
is the most sensitive configuration to capacitive load. Direct
capacitive loading reduces the phase margin of op-amps.
The combination of the op-amp’s output impedance and the
capacitive load induces phase lag. This results in either an
underdamped pulse response or oscillation.
Capacitive load compensation can be accomplished using
resistive isolation as shown in Figure 7 . If there is a resistive
component of the load in parallel to the capacitive compo-
nent, the isolation resistor and the resistive load create a
voltage divider at the output. This introduces a DC error at
the output.
Figure 8 displays the pulse response of the LMC6582 circuit
in Figure 7 .
FIGURE 7. Resistive Isolation of a 350 pF Capacitive
FIGURE 6. An Input Voltage Signal Exceeds
V
S
LMC6582/4 Power Supply Voltages of
= 1.8V with No Output Phase Inversion
FIGURE 8. Pulse Response of the
LMC6582 Circuit in Figure 7
Load
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S
=