Violectric HPA V280 User Manual page 20

The input signals are fed to the loads via two amplifiers per load. The trick is,
that one of these amplifiers is working "normal", the other inverted respectively
0
180 phase shifted.
While one amp is "pushing", the other amp is "pulling". In doing so the output
amplitude is doubled and the power is fourfold compared to a "normal" amp with
the same supply voltage.
Unfortunately the real life is not as easy as the above simple schematics.
Here is the "normal" amp with problem zones:
Besides the load, which has to be driven there are several other impedances
which should be taken into account. All these are able to impair the proper
driving of the load.
Impedances are a complex mix of resistive, capacitive and inductive parameters
which may lead to an instable operation of an amp when the capacity of a cable
is too high.
To keep things simple, for the following examinations only the resistive parts
shall be taken into account.
Every above resistive load will cause a voltage drop which is responsible for a
none-linear behavior inside the system.
Some problems are apparent at first glance:
·
The higher the resistive load, the lower the parasitic impedance
influences
·
The lower the resistive load, the higher the parasitic impedance
influences
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