| 摘要 |
PURPOSE:To attain frequency conversion from a very minute current region over a wide variety, by using a diode as a switching element and decreasing the leakage current of the switching element. CONSTITUTION:The potential of an output terminal OUT of a monostable multi- vibrator 27 is kept at -Vss at an arbitrary time t1 at which no positive pulse is outputted, and the 2nd diode 22 is set on. In this state, the current outputted from a constant current source 23 all passes through the diode 22, an operational amplifier 25 integrates inputted electromagnetic waves for measurement only and the potential at the output terminal is increased in accordance with the integrated value. The multivibrator 27 monitors an output of the operational amplifier 25, and when the voltage reaches a threshold value VTH, a pulse 31 of a voltage +VDD is outputted for a prescribed time. In this state, the 1st diode 21 is truned on, the current outputted from the current source 23 all passes through diode 21 and a pulse having a frequency proportional to the input current is outputted at an output terminal 29. |
