| 摘要 |
PURPOSE:To eliminate the distortion generated in a three-terminal variable resistance and to make the gain variable, by grounding the middle point of this resistance through a resistance and providing a circuit, which converts an input signal to a current, in one rest terminal and providing a mirror circuit, which generates the same current, in the other terminal. CONSTITUTION:The signal inputted to transistors TR1 and TR2 constituting a complementary emitter follower circuit is converted to a current i1 having a value proportional to the reciprocal of the sum between a resistance R3 connected to emitters and a resistance R4 in the side of one terminal of a tree-terminal variable resistance 7. The current i1 is outputted as a current i2, which has the same value as the current i1 and has the direction opposite to that of the current i1, from an output terminal B by inversion current mirror circuits 5 and 6. The current i2 is outputted as a voltage proportional to an impedance element Z2 and a resistance R5. The current flowed to the variable resistance 7 can be ignored because it corresponds to the difference between currents i1 and i2, and distortion is not generated for the output. |
