3. Dynamic Bias Control Alternate
Implementation
Phone designers can use
TX_ADC_ADJ pin of the
the PA. The variable output levels
from two inverting operational
amplifiers, generated and
compared by TX_ADC_ADJ,
provide dynamic control voltages
baseband IC to get dynamic bias
control with Vcntl pin of PA.
TX_ADC_ADJ is a PDM output
pin produced by the TX AGC
subsystem and used to control
the gain of the Tx signal prior to
for the Vcntl of 1.0V 2.7V with
~
a 0.1V step.
Battery
Vbias
Vdd2
Vdd1
To Duplexer
PA
Vcntl
TxIC
Baseband IC
Vcontrol
Enable
PA_ON
Switch Circuit
R1
R3
_
R5
TX_ADC_ADJ
_
Vin
R2
C1
V1
+
R4
Av = -(V1/Vin) = -R3/R2,
V1 = -(R3/R2)Vin,
Vo = -(R5/R4)V1= [(R5 R3)/(R4 R2)] Vin
*
*
*
The using of combination of two
pins, PDM1 and TX_ADC_ADJ, is
another method of realizing a
dynamic bias control scheme.
The two OP Amps control the
Vcntl voltage levels with com-
pared and integrated circuits.
Battery
Vbias
Vdd2
To Duplexer
Vdd1
TxIC
PA
Baseband IC
Vcntl
Vcontrol
Enable
PA_ON
Switch Circuit
_
TX_ADC_ADJ
_
+
+
PDM1
13
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
