User's Manual

EXHIBIT 2 PAGE 14 OF 17
TX RX Systems Inc. Manual 7-9257 (version 1) 11/03/00 Page 14
Repair or replacement of bias circuit components
does not necessitate retuning of the amplifier.
First Driver Amplifier 3-11432
The remaining four stages of the five stage assem-
bly (3-11432) are used to form a driver amplifier
which amplifies the output of the OLC assembly
and applies it to the second driver amp.
Second Driver Amplifier 3-11795
The second driver amplifier is used to provide suffi-
cient amplification to drive the input of the final
amp. It uses a single ultra-linear RF transistor. The
2.5 watt rating indicates the maximum safe output
from this amplifier using a single carrier. The
actual maximum allowable power output with multi-
carriers is considerably lower and is determined by
the maximum allowable intermodulation product
level and is also limited by the collector-emitter
breakdown rating of the RF transistor.
This amplifier stage draws a nominal 500 ma. A
bias regulator circuit within the amplifier assembly
is used to keep the collector current of the RF tran-
sistor constant with changes in temperature. This
amplifier has a minimum gain of 14 dB, 15 dB typi-
cal. The amplifier uses narrow band matching tech-
niques and will require tuning if the transistor or
matching network components are replaced.
The bias regulator circuit uses an operational
amplifier and a PNP transistor to supply a variable
bias current that varies as required to keep the RF
transistor collector current constant. Current to the
collector of the RF transistor is sampled through
resistor R5. The voltage at the collector side of this
resistor is applied to the non-inverting input of U1.
Voltage divider R6 / R7 sets the desired reference
voltage on the inverting terminal of U1. U1 is lifted
above chassis ground by the zener diode D2 in
order to keep U1 operating below its 18 volt maxi-
mum rating.
Resistor R3 and C2 work in combination to pre-
vent U1 from oscillating at audio frequencies. The
variable output voltage of U1 biases pass transistor
Q1 through the voltage divider R4 / R8. Q1 in turn
supplies the current to bias the RF transistor. The
bias on the RF transistor varies in such a way as to
keep the voltage at the collector end of R5 equal to
the reference voltage provided by divider R6 / R7,
thus keeping the RF transistor's collector current
constant. Repair or replacement of bias circuit
components does not necessitate retuning of the
amplifier.
Power Amplifier 3-3948
This 6 watt final amplifier uses a single ultra-linear
RF transistor. The 6 watt rating indicates the maxi-
mum safe power output from this amplifier using a
single carrier. The actual maximum allowable
power output with multi-carriers is considerably
lower and is determined by the maximum allowable
intermodulation product level and is also limited by
the collector-emitter breakdown rating of the RF
transistor. The One-Way Signal Booster systems
power specifications appear on the specification
drawing.
This stage receives its DC power from the 21 volt
regulator and draws a nominal 960 ma. The RF
transistor is biased for a nominal collector current
of 880 ma. A bias regulator circuit is used to keep
the collector current constant with changes in tem-
perature. This stage has a minimum gain of 9 dB,
10 dB typical. This amplifier uses narrow band
matching techniques and will require tuning if the
transistor or matching network components are
replaced.
The bias regulator circuit uses an operational
amplifier and a PNP transistor to supply a variable
bias current that varies as required to keep the RF
transistor collector current constant. Current to the
collector of the RF transistor is sampled through
resistor R5. The voltage at the collector side of this
resistor is applied to the non-inverting input of U1.
Voltage divider R6 / R7 sets the desired reference
voltage on the inverting terminal of U1. U1 is lifted
above chassis ground by the zener diode D2 in
order to keep U1 operating below its 18 volt maxi-
mum rating.
Resistor R3 and C2 work in combination to pre-
vent U1 from oscillating at audio frequencies. The
variable output voltage of U1 biases pass transistor
Q1 through the voltage divider R4 / R8. Q1 in turn
supplies the current to bias the RF transistor. The
bias on the RF transistor varies in such a way as to
keep the voltage at the collector end of R5 equal to
the reference voltage provided by divider R6 / R7,
thus keeping the RF transistor's collector current
constant. Repair or replacement of bias circuit
components does not necessitate retuning of the
amplifier.