User Guide

Technical Documentation
NHD–4
System Module
P.A.M.S
Page 4–35
Original 11/97
VRX
VRX is used to supply the LNA (V12) and the LNA switches (N701, N702).
It is also biases the RX_LO gain stage (N704) at the UHF synthesizer
module. VRX will be approximately 4.45 V while active in AMPS RX/TX
mode.
VRXA
VRXA is used for AMPS RX applications such as bias for the AMPS RX IC
(D1) and the 1
st
IF gain stage while in AMPS operation. VRXA will be
approximately 4.45 V when active.
VRXD
VRXD will be approximately 4.45 V while active.
VRXD_R
Both the CDAGCR IC (N1) and the CDMA IF LNA (V7) are biased from
this supply. The 1
st
IF gain stage (V9) is also biased from this supply.
N706 is a voltage regulator IC providing 4.50 V at pin 4 when enabled at
pin 1.
VRXS
VRXS is used to bias the PLL IC (N300) and the 15.36 MHz VCTCXO
(G300). VRXS should be approximately 4.45 V when active in the AMPS
RX/TX mode.
VRX90
VRX90 is used to bias the 180 MHz VCO and buffer amp. VRX90 should
be approximately 4.45 V when active in the AMPS RX/TX mode.
VTX
VTX is used in transmitter applications, mainly for biasing the CDAGCT IC
(N100).
Just like the VBBFIL, the VTX supply circuit uses an external PNP
transistor (V202) for regulation. The resistors R201 and R202 are used
as part of this external regulator circuit. This supply is on whenever the
transmitter is on. When this supply is active, the collector of V203 will be
approximately 5.30 V, the emitter will be VBAT, the battery voltage, and
the base of V203 will be approximately 0.7 V down from the emitter.
VTXS
VTXS is used in transmitter applications such as bias for the AT–109
variable attenuator (V106) and bias to the Detector (V114). This supply
also biases the negative voltage generator (N200) which creates VNEG.
VTXS will be approximately 4.45 V when active in the AMPS RX/TX mode.