| 摘要 |
PURPOSE:To accelerate a time to start the operating state of a current mirror circuit, by permitting a microcurrent which causes no problem to flow on the current mirror circuit at the time of cutting off the circuit. CONSTITUTION:A current switching circuit consists of transistors Q7, Q8, Q10, and Q20, and an npn transistor having a transition frequency ftau and a current amplification factor B superior than that of a general npn transistor is used, and it is possible to perform switching control at high speed by setting a control voltage Vin as a switching pulse P3. Furthermore, when the transistor Q20 is cut off, the current mirror circuit of the Q7 and Q8 is expected to be set at a cut off state from an idealistic viewpoint, however, a potential (n-1)VBE exists on the emitter of a transistor Q9 actually because the potential of the Q9 goes to nVBE actually, and the microcurrent which causes no problem is permitted to flow on the current mirror circuit. Therefore, it is possible to accelerate the time to set the operating state of the current mirror circuit after the Q20 is turned ON. |
