Datasheet

LM4853

SNAS155E –JANUARY 2002–REVISED MAY 2013

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The high frequency pole is determined by the product of the desired high frequency pole, f

, and the differential

gain, A

. With A

= 3 and f

= 100kHz, the resulting GBWP = 150kHz which is much smaller than the LM4853

GBWP of 10MHz. This difference indicates that a designer can still use the LM4853 at higher differential gains

without bandwidth limitations.

PCB LAYOUT AND SUPPLY REGULATION CONSIDERATIONS FOR DRIVING 3Ω AND 4Ω

LOADS

Power dissipated by a load is a function of the voltage swing across the load and the load's impedance. As load

impedance decreases, load dissipation becomes increasingly dependant on the interconnect (PCB trace and

wire) resistance between the amplifier output pins and the load's connections. Residual trace resistance causes

a voltage drop, which results in power dissipated in the trace and not in the load as desired. For example, 0.1Ω

trace resistance reduces the output power dissipated by a 4Ω load from 2.0W to 1.95W. This problem of

decreased load dissipation is exacerbated as load impedance decreases. Therefore, to maintain the highest load

dissipation and widest output voltage swing, PCB traces that connect the output pins to a load must be as wide

as possible.

Poor power supply regulation adversely affects maximum output power. A poorly regulated supply's output

voltage decreases with increasing load current. Reduced supply voltage causes decreased headroom, output

signal clipping, and reduced output power. Even with tightly regulated supplies, trace resistance creates the

same effects as poor supply regulation. Therefore, making the power supply traces as wide as possible helps

maintain full output voltage swing.

Demonstration Board Layout

Figure 40. Recommended MM PC Board Layout:

Component-Side SilkScreen

Product Folder Links: LM4853