| 摘要 |
A variable gain amplifying circuit is disclosed, which comprises a first transistor pair whose bases are connected to input terminals, a PN junction pair with bias currents that are collector currents of the first transistor pair, a second transistor pair with a common emitter that is a base input of a voltage difference of the PN junction pair, the common emitter having a current source, and a third transistor pair whose collectors are connected to corresponding emitters of the first transistor pair, whose bases are connected to the corresponding collectors, whose emitter are connected through a resistor, and whose emitters are connected to a current source for supplying bias currents, wherein outputs are obtained from the collector of the second transistor pair.
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