| 摘要 |
<p>A variable gain amplifier includes first and second power supply terminals arranged to be connected to a power supply, a transconductance amplifier, first and second PN junction elements, a voltage drop element, first and second resistors, a current-generating transistor, and a current mirror. The transconductance amplifier outputs a current corresponding to a difference between a potential of a base of the first initial stage transistor and a potential of a base of the second initial stage transistor. An emitter of the second initial stage transistor is connected to the emitter of the first initial stage transistor at a node. Each of the first and second PN junction elements has a first end connected to the base of the first initial stage transistor and a second end. The voltage drop element is connected between the second end of the first PN junction element and the first power supply terminal. The first resistor is connected between the base of the second initial stage transistor and a first signal source which is a voltage source. The current-generating transistor has a collector connected to the base of the first initial stage transistor and a base connected to the first signal source. The second resistor is connected between the emitter of the current-generating transistor and the second power supply terminal. The current mirror is connected to the node, and allows a current to flow to the node, the current being identical to a current flowing from the second signal source which is a current source. This variable gain amplifier generates no non-linear distortion, and has a small size.</p> |
