| 摘要 |
PURPOSE:To decide the variable gain range depending on the emitter area ratio by providing one set of resistors deciding the gain and also providing a current dividing circuit comprising transistors (Tr) having a prescribed emitter area. CONSTITUTION:When the driving voltage is given as VC1>VC2, a TrQ10 is turned on and Trs Q11, Q12 are turned off, then a signal current ic flows all via a load resistor RL. In case of VC1<VC2, the TrQ10 is turned off and the Trs Q11, Q12 are turned on. The relation of iC1=N.ic/(1+N), iC2=ic/(1+N) is obtained, where iC1 is a signal current flowing to the load rasistor RL in the signal current ic and iC2 is other signal current and N is the emitter area ratio of the TrQ11 to the Q12. Thus, the voltage gain AV2 is decided by the N and an optional gain range is selected. |
