A general voltage amplifier (Voltage-to-Voltage) is explained as follows.
A preamplifier has two types: one has a single signal-input terminal, and the other has a total of two input terminals (one positive and one negative).
A single-input terminal amplifies the potential difference from the ground potential (ground, GND), and it is called a single-ended system [(a) in the figure below]. In the case of a coaxial terminal (BNC connector, SMA connector, etc.), the core-wire side is the signal wire, and the outer-skin side is the ground potential.
On the contrary, a preamplifier with positive and negative inputs is called a differential system. It amplifies the difference between the positive input (+) and the negative input (-) [(b) in the figure]. If one side of the differential input is connected to the ground potential, the same system as the single-ended one is created [(c) in the figure].
The general differences between the three systems, i.e., single-ended, differential, and differential with single-wire grounding, are summarized below in the Table.
|System||Single-ended||Differential||Differential with single-wire grounding|
|Input line||One signal line is enough.||Two signal lines are required.||One signal line is enough.|
|Distance between signal lines||Limited to a short distance.||Also supports long distances||Limited to a short distance.|
|Inversion of amplification polarity||Impossible||Possible||Possible|
Related keywords : Ultra low noise amplifier, LNA