MC13176D View Datasheet(PDF) - LANSDALE Semiconductor Inc.

Part Name

Description

Manufacturer

MC13176D

UHF FM/AM Transmitter

LANSDALE Semiconductor Inc. 

ML13175/ML13176

LANSDALE Semiconductor, Inc.

Legacy Applications Information

Figure 23. Power Output versus Modulation Current

10

5.0

0

– 5.0

VCC = 3.0 Vdc

f = 320 MHz

–10

–15

– 20

– 25

0.1

1.0

10

Imod, MODULATION CURRENT (mA)

ANALOG AM

In analog AM applications, the output amplifier’s linearity

must be carefully considered. Figure 23 is a plot of Power

Output versus Modulation Current at 320 MHz, 3.0 Vdc. In

order to achieve a linear encoding of the modulating sinu-

soidal waveform on the carrier, the modulating signal must

amplitude modulate the carrier in the linear portion of its

power output response. When using a sinewave modulating

signal, the signal rides on a positive DC offset called Vmod

which sets a static (modulation off) modulation current,

Imod. Imod controls the power output of the IC. As the mod-

ulating signal moves around this static bias point the modu-

lating current varies causing power output to vary or to be

AM modulated. When the IC is operated at modulation cur-

rent levels greater than 2.0 mAdc the differential output stage

starts to saturate.

Page 14 of 16

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