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February 007 Page 7 of 17 Revision C
Chapter 3 Technical Description
3 1 GENERAL DESCRIPTION
The E&I Model 3 5LA is a linear Class A amplifier capable of increasing the output of any
signal generator, frequency synthesizer, sweep generator or laboratory signal source
from 50 kHz to 150 MHz. The Model 3 5LA is completely protected against damage due
to load mismatch provided that the input RF level does not exceed 1 VRMS or 1.4V peak.
If the attached signal source is capable of generating substantially more than this input
voltage, please use caution in adjusting it. The Model 3 5LA will saturate well before the
maximum input voltage and there will be no increase in output power at that point. The
3 5LA is unconditionally stable. Any impedance can be connected to the input and output
of the amplifier, without causing oscillation. The 3 5LA will deliver its rated power to any
load impedance regardless of match. Load mismatch will cause RF power to reflect back
to the amplifier. The unit is designed to withstand 100% reflected power (a pure
reactance open or short circuit load will cause 100% reflected power) continuously
without damage. An output meter is provided to indicate the average forward and
reflected power (RMS). Since the meter responds only to average power, the modulation
characteristics of the input signal must be taken into account when interpreting the meter
readings. For example, the amplifier may be in saturation during the ON portion of a pulse
yet the meter reading will be low due to the low duty cycle of the pulse input.
3 2 Control, Indicators and Connectors
The power switch is located on the front panel.
The BNC connectors are marked with the universal symbol for input and output.
The Back Lit LCD display indicated forward and reverse power in addition to the status.
3 3 Operating Procedure
Refer to the following procedure as a guide to operating the Model 3 5LA.
a. The input and output are connected via the front panel BNC connectors to the signal
source and load respectively.
b. The input signal should be increased gradually while observing the output voltage on
the output RF voltmeter.
c. When the Model 3 5LA is connected to a 50Ω load, the CW power output of the unit
may be read directly from the Display.
See Figure 2 for Front and Rear panel
