| 摘要 |
PURPOSE:To remove the change of characteristics due to the vibration of power voltage and temperature by using in common the bias of the constant current source of differential amplifiers which are constitutional elements when an amplifying stage is coupled with a comparing stage in series. CONSTITUTION:An input signal Vi is applied to an input transistor 9, which composes a clamp circuit 3, and the 1st differential amplifier 10 through a coupling capacitor to obtain a video signal in which the top level of a synchronous signal is constant. The video signal is applied to the 2nd differential amplifier 13 composing an amplifier 12 to be amplified and then applied to the 3rd differential amplifier 18 composing a comparing means 4. At that time, the bases of constant current transistors 23-25 connected to the sides of respective emitters for constant current sources of the 2nd and 3rd differential amplifier 13, 18 are connected in common with the emitter of the 2nd bias transistor 27 connected to a bias means 26. Thus, the entitled circuit can be prevented from the change of characteristic due to the variation of power voltage and temperature by adjusting the value of resistances to satisfy a prescribed relation. |
