Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
This article describes a comparator with a single power supply which is used as a zero detector. This comparator comprises an operational amplifier with a feedback path from its output to a positive input through a resistor. Fig. 1 shows the circuit configuration of the comparator consisting of an operational amplifier, six resistors R1 - R6, a diode D, and a power supply V. This circuit is characterized by the resistor R3 connected between the positive and negative inputs of the operational amplifier. When the output of the operational amplifier is high, a biasing current I flows upward through the resistor R3. Therefore, the output remains high until an input waveform, such as shown in Fig. 2, reaches some positive value. Assuming R1 = 3K, R2 = 6K, R3 = R5 = R6 = 1K, R4 = 10K and V = 5 volts, this value is about 4.2 volts.