In engineering testing, we occasionally encounter a tricky problem: the output power of a single high-voltage amplifier cannot meet the driving requirements of extreme loads. A seemingly straightforward solution popped into my mind - by paralleling the outputs of two or more identical amplifiers, wouldn't it be easy to obtain double or even multiple times the current and power? But this is an extremely dangerous and wrong idea! Simply connecting the amplifier outputs in parallel can easily cause expensive equipment damage and even jeopardize testing safety in an instant.

Ideally, two identical amplifiers connected in parallel should evenly distribute the load current. But in the real world, no two amplifiers are completely identical. This small difference will be rapidly amplified in the context of high voltage and high current, mainly causing two fatal problems:

1. Circulation problem | "internal friction" between amplifiers

Root cause: Small differences in output voltage. Even if two amplifiers are set to the same gain and input voltage, there may still be slight errors in their actual DC offset and output voltage amplitude. Assuming that the output voltage of amplifier A is 0.1V higher than amplifier B.

Consequence: This 0.1V difference will not affect the load, but will form a huge short-circuit current loop between amplifiers A and B. This current does not flow to the load and only 'idles' inside the two devices, which we call' circulating current '.

Destructive: Due to the extremely low output impedance of the amplifier, this circulating current will be very large, far exceeding its normal output current capacity. The result is either an emergency shutdown of the amplifier due to overcurrent protection, or permanent burnout of the power device due to instantaneous overheating.

2、The problem of equal flow | The tragedy of 'the capable work harder'

Even if we manage to eliminate the DC bias and make the no-load output voltage of the two amplifiers exactly the same, once the load is connected, the problem will reoccur.

Root cause: Differences in output impedance. The output impedance of each amplifier always has slight differences. An amplifier with slightly lower output impedance will exhibit "stronger" driving capability when loaded.

Consequence: In parallel, the amplifier with lower output impedance will automatically bear more current, while the other one will bear less. This breaks the ideal uniform current state. The amplifier that carries more current will overheat first, enter overcurrent protection state in advance or be damaged. Subsequently, all load currents will instantly transfer to the remaining amplifier, ultimately leading to a chain like comprehensive failure.

Conclusion and Action Guidelines

Do not attempt to directly parallel the output terminals of the high-voltage amplifier on your own! The success rate of this operation is infinitely close to zero, but the cost is extremely high.