Table of Contents
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1. INTRODUCTION
The 2707 is a Power Amplifier designed to drive highly reactive loads,
such as small vibration exciters, and particularly the Exciter Body Type
4801 and the associated heads. The amplifier has a useable frequency range
from
DC
to
100kHz and
full
output
(220 VA)
over the range
40Hz-10kHz.
Current or voltage mode negative feedback can be used, giving a highly
linear output and a selectable output impedance. The amplifier can be oper-
ated as a low output impedance voltage generator or as a high output
impedance current generator.
The output is directly coupled to provide static table centring and to
exclude bulky output transformers.
As well as power amplification, the 2707 provides monitoring, con-
tinuous metering and protective functions. The RMS values of the moving
coil voltage and current are continuously shown on front panel meters and
the associated waveforms can be monitored using the oscilloscope connect-
ors provided.
Fast acting protective circuitry gates off the signal input to the amplifier
if pre-set moving coil current and exciter head displacement limits are
exceeded. The protection is also triggered by excessive temperature rise of
the output transistors in the amplifier. On shut-down the relevant front
panel fault indicator is lit. Any clipping of the output voltage, caused by too
high
a driving voltage or output current peaks, and any power transistor
failures are also indicated.
5
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