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 Lecture for Measurement

Posted 2019/7/19

Voltage amplifier ("voltage to voltage amplifier")

What is a voltage amplifier ("voltage to voltage" amplifier)?

A general voltage amplifier (voltage to voltage amplifier) is explained as follows.

1. Single-ended ground and differential

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 in 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

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