Posted 2019/7/19
A general voltage amplifier (voltage to voltage amplifier) 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].
Figure
The general differences between the three systems, i.e., single-ended, differential, and differential with single-wire grounding, are summarized in Table.
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. |
| Common-mode noise | Influenced | Reducible | Affected |
| Inversion of amplification polarity | Impossible | Possible | Possible |
Related keywords : Ultra low noise amplifier, LNA
