Application information

STPAC01F2

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Figure 9.

2

Application information

Figure 10.

Application diagram

The STPAC01 is the first part of the power amplifier stage and provides both RF power and

die temperature measurements. Figure 10 shows the basic circuit of RF detector.

A coupler located on the line between RF amplifier output and the antenna takes a part of

the available power and applies it to STPAC01 RF input.

The RF detector and the low-pass filter provide a DC voltage depending on the input power.

Thermal compensation provides a DC voltage depending on the ambient temperature. As

the detection system and the thermal compensation are based on the same topology,

VDCout will have the same temperature variation as Vtemp. Connected to a differential

amplifier, the output will be a voltage directly linked to the RF input power. VDCout and

Vtemp must be biased with 50 µA DC current.

This topology offers the most accurate output value as it is 100% compensated.

1.88

1.9

1.92

1.94

1.96

1.98

0

1020

30

40

50

6070

Tamb (°C)

Vtemp

Ibias = 50µA

Coupler

GND2

Out

GND1

STPAC01F2

RF input

Thermal

compensation

Low pass

filter

RF detector

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+