| 摘要 |
PURPOSE:To linearize the control voltage-gain characterisics, by inserting a transistor to a diode and supplying the input signal voltage given from an input signal source to the emitter of a current source transistor. CONSTITUTION:It is possible to set the DC voltage of a signal output terminal 11 at a fixed level owing to the function of a dummy circuit 22 despite variations of control voltage VC since diodes D an D' are inserted to the emitters of transistors TRQ2 and Q2' having a base common with each other. While input signal voltage ei is converted into a signal current I0 as shown by i0=ei/Ri if signal current i0 flowing to a constant current source 21 from an input signal source 14 via an input resistance Ri is much less than the current IO of a constant current source 21. Then the signal current i0 flows to TRQ1 and Q2 with a shunt ratio which is decided by the control voltage VC, and output signal voltage e0 is generated by a signal current i1 which flows to a load resistance RL. The gain control characteristics of this circuit depend approximately on a linear equation of the current I1 of the TRQ1 and becomes linear. |
