| 摘要 |
PURPOSE:To surely generate a trigger circuit by a circuit wherein the peak value of output voltage of an amplifier and the hysteresis level of a Schmitt trigger circuit are detected, and the difference between the peak value and the hysteresis level is used to adjust a DC level of the amplifier. CONSTITUTION:The difference between voltages applied to bases of transistors 12, 13 of a DC amplifier 11 is amplified and output to collector of a transistor 14. A peak value detection circuit 23 detects upper and lower limit values of output voltage of the DC amplifier 11 and provides an output representing the average value thereof. An average-value output of hysteresis levels of a Schmitt trigger circuit 36 is obtained through resistors 34, 35 and applied to an error difference amplifier 33 together with the upper and lower peak values. The difference in average value between the peak value and the hysteresis level is applied to base of the transistor 13, and the level of the amplifier 11 is varied so that the difference voltage becomes zero. With this arrangement, it becomes possible to surely operate a sweeping circuit independently of a DC level of the input signal. |
