| 摘要 |
PURPOSE:To prevent the fluctuation of a threshold voltage by applying a threshold voltage of a TTL level to the base of a 2nd bipolar transistor(TR) having the same characteristic with a 1st bipolar TR inputting an input signal as a reference voltage. CONSTITUTION:Emitters of PNP TRs Q1, Q2 are connected to a power supply VCC via a constant current source 4 receiving a constant current ICS. A TTL level threshold voltage VTH is applied to the base of the TR Q2 from a reference voltage generating circuit stable against the power voltage and temperature or the like. The TR Q1 receiving the input signal and the TR Q2 receiving the threshold voltage VTH of the TTL level and having the same characteristic as that of the TR Q1 are operated differentially. Thus, the fluctuation of the forward base-emitter voltage of the TR Q1 is cancelled, the threshold voltage VTH is made stable to ensure stable noise margin. |
