Benefon DRAGON TDP70WN, Service Manual

Page: 32 / 76

5.9.2000
4Z2200GB.fm 15
Product: TDP70WN / OC2285 Processor/Audio/RF
5.6 TRANSMITTER
5.6.1 General
5.6.2 Function Description
The transmitter unit is comprised of three amplifier stages and two attenuator
stages. The pre-amplifier Q620/Q621 and power module I650 form the transmitter
amplifier chain. The attenuators surrounding the pre-amplifier are included to
enhance the electric separation between the TX synthesizer and the transmitter.
The operational amplifier I640 and transistors Q641 and Q642 serve as a power reg-
ulator circuit, which adjusts the power level so that the voltage from the transmitter
power detector (D660) and the control voltage TXPWR from the audio/processor
unit are equal.
The negative bias voltage for the power amplifier is generated from the 13 MHz
TCXO signal.
I610 amplifies the signal for the switched power supply Q610/D610 and is then regu-
lated by the zenerdiode D611.
I600 serves as voltage regulator for pre-amplifier and for the negative voltage
generetor.
Q631 serves as the ON/OFF switch for the output power.
5.6.3 Control- and Output-Signals
Operating voltage 3.5 ... 4.5 v
Current consumption mid power max. 1.1 A
low power max. 0.45 A
Input level from the synthesizer +6 dBm
Output level to the duplex filter mid power 33 dBm (2.0W)
low power 24.7 dBm (0.3W)
Frequency range 453.000...457.475 MHz
VBAT
Transmitter operating voltage from the
battery-pack (fused)
TXBIAS Power ON/OFF control
TXPWR
Power level control signal from the D/A
converter
0...3V
TXINJ RF signal from the TX synthesizer +6dBm
TXDUPLEX Transmitter output to the duplex filter