| 摘要 |
There is provided an amplifier circuit includes: an amplifying transistor; a first transistor having a DC current amplification factor generally equal to the DC current amplification factor of the amplifying transistor and constituting a current mirror circuit in conjunction with the amplifying transistor; and a current source circuit being operable to supply a current to the first transistor and including a second transistor having opposite conductivity type to the conductivity type of the first transistor. The second transistor is operated in a saturation region at a power supply voltage lower than an operating voltage range so that the DC current amplification factor of the amplifying transistor can be detected.
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