-IN

+IN

RF Power Amplifier

LMP8278

+

-

A1

A2

Internal

Resistor

100 k:

C1

OUT

8

5

3

4

1

Preamplifier

Gain = 7

Output Buffer

Gain = 2

24V

Controller

0.02:

LMP8278

+

-

Preamplifier

Output Buffer

Gain = 2

A1

A2

Gain = 7

Internal

Resistor

100 k:

C1

POWER

SWITCH

INDUCTIVE

LOAD

+IN

-IN

OUT

0.01

Ö

1

5

3

4

8

24V

LMP8278

SNAS575A – FEBRUARY 2012 – REVISED MARCH 2013

www.ti.com

Figure 28. High Side Current Sensing Application

RF-PA CONTROL APPLICATION

Figure 29 illustrates how the LMP8278 can be used to monitor current flow in an RF power amplifier control

application. The fact that the LMP8278 can measure small voltages at a high common mode voltage outside its

own supply range makes this part a good choice for such an application. The output signal of the LMP8278 is

used as an input for the PA controller. The PA controller can be used to regulate the output power of the RF-PA

by measuring the output amplifier supply current.

Figure 29. RF Power Amplifier Control Application

16

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