LME49721MAX/NOPB National Semiconductor, LME49721MAX/NOPB Datasheet - Page 16

• Manufacturer Part Number: LME49721MAX/NOPB
• Description: IC AMP AUDIO STER AB HIFI 8SOIC
• Manufacturer: National Semiconductor

Specifications of LME49721MAX/NOPB

• Amplifier Type: Audio
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 8.5 V/µs
• Gain Bandwidth Product: 20MHz
• Current - Input Bias: 0.04pA
• Voltage - Input Offset: 300µV
• Current - Supply: 2.15mA
• Current - Output / Channel: 9.7mA
• Voltage - Supply, Single/dual (±): 2.2 V ~ 5.5 V, ±1.1 V ~ 2.75 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• For Use With: LME49721MABD - BOARD EVAL FOR LME49721
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Other names: LME49721MAX

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Application Information
DISTORTION MEASUREMENTS
The vanishingly low residual distortion produced by
LME49721 is below the capabilities of all commercially avail-
able equipment. This makes distortion measurements just
slightly more difficult than simply connecting a distortion me-
ter to the amplifier's inputs and outputs. The solution. howev-
er, is quite simple: an additional resistor. Adding this resistor
extends the resolution of the distortion measurement equip-
ment.
The LME49721's low residual is an input referred internal er-
ror. As shown in Figure 1, adding the 10Ω resistor connected
between athe amplifier's inverting and non-inverting inputs
OPERATING RATINGS AND BASIC DESIGN GUIDELINES
The LME49721 has a supply voltage range from +2.2V to
+5.5V single supply or ±1.1 to ±2.75V dual supply.
Bypassed capacitors for the supplies should be placed as
close to the amplifier as possible. This will help minimize any
inductance between the power supply and the supply pins. In
addition to a 10μF capacitor, a 0.1μF capacitor is also rec-
ommended in CMOS amplifiers.
The amplifier's inputs lead lengths should also be as short as
possible. If the op amp does not have a bypass capacitor, it
may oscillate.
BASIC AMPLIFIER CONFIGURATIONS
The LME49721 may be operated with either a single supply
or dual supplies. Figure 2 shows the typical connection for a
single supply inverting amplifier. The output voltage for a sin-
gle supply amplifier will be centered around the common-
mode voltage Vcm. Note, the voltage applied to the Vcm
insures the output stays above ground. Typically, the Vcm
FIGURE 1. THD+N and IMD Distortion Test Circuit with A
16
changes the amplifier's noise gain. The result is that the error
signal (distortion) is amplified by a factor of 101. Although the
amplifier's closed-loop gain is unaltered, the feedback avail-
able to correct distortion errors is reduced by 101. To ensure
minimum effects on distortion measurements, keep the value
of R1 low as shown in Figure 1.
This technique is verified by duplicating the measurements
with high closed loop gain and/or making the measurements
at high frequencies. Doing so, produces distortion compo-
nents that are within equipments capabilities. This
datasheet's THD+N and IMD values were generated using
the above described circuit connected to an Audio Precision
System Two Cascade.
should be equal to V
divider ckt at this node, see Figure 2.
FIGURE 2. Single Supply Inverting Op Amp
DD
/2. This is done by putting a resistor
V
= 2
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