PCR is the acronym for polymerase chain reaction, which is a gene amplification technique, and the instrument that applies this technique is called PCR instrument, or gene amplifier. Ordinary PCR instrument is qualitative (need to be analyzed by electrophoresis after amplification), fluorescence quantitative PCR instrument can be quantitative (with the addition of fluorescent probe).
Usually when we say gene amplifier, we mean regular PCR.
Usually, the term gene amplifier refers to an ordinary PCR instrument.