Part 3 : The P.A. Circuit and its Control
Fig.8: The Power Amp Circuit
The P.A Circuit and its control
The power amplifier control circuit ensures that the RF signal is regulated to the
required limits of operation.
The TX RF signal is input on #1(IC106) or (IC107) and the power amplifier outputs
the signal at #4.
IC105 and IC108 are op-amps, which output a control signal to the P.A.
Power control is carried out by measuring the current drawn by the P.A (see
Fig.9:
P.A Circuit Control
). The current drawn by the P.A. is directly proportional to the
output power and is measured as a voltage drop across a known resistance path
or “Fixed Control Loop Stripline”. This consists of a 47mOhm resistor (R144) for
GSM or two resistors in series, a 47mOhm (R144) and 27mOhm (R136) for PCN.
The voltage drop (V_ERROR) is then integrated by the operational amplifier
(IC108) to give an error voltage, which regulates the TXP signal.
The TXP input signal to the power control circuit is generated by the IC27 #90. TXP
provides a limit for the frequency spectrum caused by burst modulation.
BPF
GSM = (890-915MHz)
PCN = (1710-1785MHz)
PA
(FL106)
(IC106)
(IC103)
BPF
PA
(IC104)
(FL105)
PCN_PRE_ON
GSM_PRE_ON
mech
switch
To Antenna
Diplexor
(IC105)
(IC108)
TXP_MOD
V_ERROR
V_ERROR
(IC107)
From IC101
TXP_MOD
From IC102
(FL103)
Summary of Contents for DB2000
Page 1: ...DB2000 Service Manual Help ...
Page 3: ... ...
Page 5: ... 2 3 4 2 2 2 2 2 0 0 0 5 3 4 2 6 2 7 2 2 2 2 0 8 9 2 2 2 2 2 2 2 2 ...
Page 7: ... 2 6 2 2 2 2 2 3 4 2 2 0 2 ...
Page 8: ... 2 ...
Page 9: ... Previous Section Next Section Main Menu Section 2 Unit Specifications ...
Page 77: ... 1 2 ...
Page 83: ...Fit Antenna INSERT AND SCREW THE ANTENNA INTO THE ASSEMBLY ...
Page 107: ...Fig 3 7 GSM_LNA Pg 3 3I TP419 Fig 3 8 PCN_LNA Pg 3 3J TP420 Fig 4 9 TCXO Pg 2 H11 TP413 ...
Page 109: ...Fig 4 3 PCN_TX Pg 1 1J TP417 Fig 4 4 3V_G_TX Pg 1 4I TP100 Fig 4 5 3V_P_TX Pg 1 4J TP101 ...
Page 110: ...Fig 4 6 GSM_ON Pg 1 2K TP402 Fig 4 7 PCN_ON Pg 1 1K TP415 Fig 4 8 PRE_ON Pg 1 4J TP416 ...
Page 112: ... I Q ...
Page 113: ...Fig 4 14 V_ERROR PCN Pwr Lvl 7Pg 1 16I Fig 4 15 300khz Charge Pump Pg 1 Log 9G ...
Page 115: ... Previous Section Next Section Main Menu Section 6 Device Device Information Information ...
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