| 摘要 |
PURPOSE:To obtain a circuit applicable to many kinds of applications, by providing a differential amplifier having symmetrical input terminals, grounding one of the two input terminals, summing an input signal to be compared and a reference signal for comparison and inputting the sum to the other input terminal. CONSTITUTION:A voltage from a Zener diode 28 is a reference voltage inverted for the polarity, and an output terminal 29 is extracted from the output by grounding one of the two input terminals of the differential amplifier 21, e.g., the inverting input terminal. The values of resistors 23, 25 and a variable resistor 22 is set so that the sum between the reference signal (voltage) for comparison obtained at a Zener diode 28 and the input signal (voltage) to be compared obtained between input terminals 24 and 27 is zero, that is, the potential at the non-inverting input of the differential amplifier 21 is 0V. Thus, if the input signal to be compared deviates from the reference signal for comparison, a level difference is caused between the two input terminals of the amplifier 21, and the differential output is extracted at an output terminal 29 as an error signal. |
