| 摘要 |
PURPOSE:To attain inexpensive DMM by constituting both circuit of a power supply voltage drop detecting circuit and an instantaneous continuity detecting circuit with an operational amplifier and two timing signals, so as to decrease the number of A/D conversion LSIs and to attain ease of large scale circuit integration. CONSTITUTION:Suppose that switches 27-30 are selected to the position A with a timing signal at first, the circuit shown in Figure acts like a power supply voltage drop detecting circuit. When a voltage given to an inverting input of an operational amplifier 24 is lower than a reference voltage VS2 as a result of voltage division with resistors 4 and 23, an output of the operational amplifier 24 jumps to the VDD and a mark 9 is lighted on a display body 26. When the switches 27-30 are selected to the position B, the circuit shown in Figure acts like an instantaneous continuity detecting circuit. When a voltage given to the inverting input of the operational amplifier 24 is smaller than a voltage VS'' given to the non-inverting input of the operational amplifier 24 in case a resistor 16 is connected between the terminal 15 and the reference level, a mark 20 is lighted on the display body 26. Thus, both of the power supply voltage drop detecting circuit and the instantaneous continuity detecting circuit are constituted with the operational amplifier and the timing signals in this way. |
