LM4890M National Semiconductor, LM4890M Datasheet - Page 20

• Manufacturer Part Number: LM4890M
• Description: 74C4636
• Manufacturer: National Semiconductor

Specifications of LM4890M

• Operational Class: Class-AB
• Audio Amplifier Output Configuration: 1-Channel Mono
• Output Power (typ): 1x1@8OhmW
• Audio Amplifier Function: Speaker
• Total Harmonic Distortion: 0.1@8Ohm@400mW%
• Single Supply Voltage (typ): 3/5V
• Dual Supply Voltage (typ): Not RequiredV
• Power Supply Requirement: Single
• Unity Gain Bandwidth Product (typ): 2.5MHz
• Rail/rail I/o Type: No
• Power Supply Rejection Ratio: 66dB
• Single Supply Voltage (min): 2.2V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• Amplifier Class: AB
• No. Of Channels: 1
• Output Power: 1W
• Supply Voltage Range: 2.2V To 5.5V
• Load Impedance: 8ohm
• Operating Temperature Range: -40°C To +85°C
• Amplifier Case Style: SOIC
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Not Compliant

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Application Information
As stated in the External Components section, R
junction with C
The high frequency pole is determined by the product of the
desired frequency pole, f
The LM4890 is unity-gain stable and requires no external
components besides gain-setting resistors, an input coupling
capacitor, and proper supply bypassing in the typical appli-
cation. However, if a closed-loop differential gain of greater
than 10 is required, a feedback capacitor (C4) may be
needed as shown in Figure 2 to bandwidth limit the amplifier.
This feedback capacitor creates a low pass filter that elimi-
C
IN
≥ 1/(2π*20 kΩ*20Hz) = 0.397µF; use 0.39µF
IN
create a highpass filter.
H
, and the differential gain, A
FIGURE 2. HIGHER GAIN AUDIO AMPLIFIER
(Continued)
IN
in con-
VD
.
20
With a A
300kHz which is much smaller than the LM4890 GBWP of
2.5MHz. This calculation shows that if a designer has a need
to design an amplifier with a higher differential gain, the
LM4890 can still be used without running into bandwidth
limitations.
nates possible high frequency oscillations. Care should be
taken when calculating the -3dB frequency in that an incor-
rect combination of R
20kHz. A typical combination of feedback resistor and ca-
pacitor that will not produce audio band high frequency rolloff
is R
-3dB point of approximately 320 kHz.
3
= 20kΩ and C
VD
= 3 and f
4
= 25pf. These components result in a
H
3
= 100kHz, the resulting GBWP =
and C
20019224
4
will cause rolloff before