LME49723MA/NOPB National Semiconductor, LME49723MA/NOPB Datasheet - Page 13

• Manufacturer Part Number: LME49723MA/NOPB
• Description: IC AMP AUDIO STER AB HIFI 8SOIC
• Manufacturer: National Semiconductor

Specifications of LME49723MA/NOPB

• Amplifier Type: Audio
• Number Of Circuits: 2
• Slew Rate: 8 V/µs
• Gain Bandwidth Product: 19MHz
• Current - Input Bias: 200nA
• Voltage - Input Offset: 300µV
• Current - Supply: 6.7mA
• Current - Output / Channel: 25mA
• Voltage - Supply, Single/dual (±): ±2.5 V ~ 17 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• For Use With: LME49723MABD - BOARD EVALUATION FOR LME49723
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• -3db Bandwidth: -
• Other names: LME49723MA

Application Information
DISTORTION MEASUREMENTS
The vanishingly low residual distortion produced by
LME49723 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, how-
ever, is quite simple: an additional resistor. Adding this
resistor extends the resolution of the distortion measurement
equipment.
The LME49723’s low residual distortion is an input referred
internal error. As shown in Figure 1, adding the 10Ω resistor
connected between the amplifier’s inverting and non-inverting
FIGURE 1. THD+N and IMD Distortion Test Circuit
13
inputs changes the amplifier’s noise gain. The result is that
the error signal (distortion) is amplified by a factor of 101. Al-
though the amplifier’s closed-loop gain is unaltered, the feed-
back available to correct distortion errors is reduced by 101,
which means that measurement resolution increases 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 the measurement equipment’s capabili-
ties. This datasheet’s THD+N and IMD values were generat-
ed using the above described circuit connected to an Audio
Precision System Two Cascade.
300362k4
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