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4.3.2 Bridge-Mono operation
By setting the back panel Dual-Mono switch to Bridge-Mono, LV 3620 is
converted to a Bridge-Mono amplifier for higher output voltage. The input
signal is applied to the Channel 1 input. The Channel 1 output then feeds the
inverting input of the Channel 2 error amp. This causes the output of
Channel 2 to be out of polarity with Channel 1 which produces twice as much
voltage across the load. The load is connected between the Channel 1 and
Channel 2 red binding posts on the back of the amplifier. Each of the
channel's protection mechanisms work independently if a fault occurs.
4.3.3 Parallel-Mono operation
In Parallel-Mono mode, twice the current of one channel alone can be
obtained. When the Dual-Mono switch is set to Parallel-Mono, the output of
Channel 2 is paralleled with that of Channel 1. The signal path for Channel 1
is the same as previously discussed, except that Channel 1 also drives the
output stage of Channel 2. The balanced input, error amp, translators and
LVAs of Channel 2 are disconnected and no longer control the Channel 2
output stage. The Channel 2 output stage and protection mechanisms are also
coupled through the Dual-Mono switch and function as one.
A suitable high-current-handling jumper must be connected across the red
binding posts to gain the benefits of this mode of operation.
The ODEP circuit of Channel 2 is coupled through the Dual-Mono switch to
give added protection if a fault occurs in the Channel 2 output stage. The
ODEP circuit of Channel 2 will limit the output of both output stages by
removing the drive from the Channel 1 translator stages.
4.3.4 Bi-Level power supply
AE Techron's patented Bi-Level power supply technology is what makes it possible to
pack such tremendous power into AE Techron's Bi-Level amplifiers.
In a linear power amplifier, the output transistors place variable resistance in series
between the load and the power supply. See Illustration 4–1. The power supply voltage
is distributed across the resistance of the output transistors and the resistance of the
load. The power supply voltage, less the voltage drop across the output transistors,
equals the output voltage to the load. The voltage drop across the transistors' resistance
dissipates power. The transistors modulate the power supply voltage, in effect, by
absorbing power and generating heat.
A power supply must be large enough to handle the maximum voltage and current
necessary for the amplifier to drive its maximum rated power into a specified load.
However, the bigger the power supply, the more heat the power transistors must
dissipate, and excessive heat is the leading cause of transistor failure.
A two-level power supply avoids much of this problem by reducing the voltage applied to
the transistors when less voltage is needed.
The Bi-Level supply is divided into segments to better match the voltage and current
requirements of the power transistors. When the voltage requirements are not high, it
operates in a parallel mode to produce less voltage and more current.
See Illustration 4–2.
Principles of Operation
LV 3620
4–4
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