MAX903CPA

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Comparators are an important component of analog circuits and are widely used in many fields of electronic engineering. MAX903CPA is a five terminal CMOS voltage comparator which has wide range of application fields. This article will introduce its application field, working principle and the related circuit diagrams.

Application field

MAX903CPA can be used in fast latch circuit and timing circuit. In the latch circuit, when it outputs high level signal, the output of it can be permanent and it keeps stably. In the timing circuit, it can be used to determine the length of the clock cycle.

The MAX903CPA can also be used as temperature control circuit and audio amplifier as well. It is widely used in medical equipment, precision measurement instruments, automotive and digital product platforms.

Working principle

The MAX903CPA has five terminals including VSS, VDD, INA, INB and OUT. INA and INB are input pins of the MAX903CPA. When the difference between INA and INB is bigger than a certain degree, the voltage potential difference between OUT and VSS terminals will have a positive feedback loop, and then the OUT terminal will be in the high level state. If the INA and INB voltages are equal, the OUT terminal will be in low level state.

Circuit diagrams

The circuit diagrams of MAX903CPA connected with a NAND gate are shown as following. INA and INB are connected to VDD and VSS respectively. When the voltage of INA is greater than the one of INB, the maximum levels of the NAND gate output will be the same as the INA voltage levels.

The latch circuit using MAX903CPA is shown as following. INA is connected to VDD and INB to the OUT terminal. When the voltage potential difference of INA and OUT is larger than the hysteresis of MAX903CPA, the OUT will be in the high level state and the signal latch. In this case, if the voltage of INA is drifting slightly, the output still keeps high level state.

The timing circuit using MAX903CPA is slightly more complex, as it needs two resistors (R1 and R2) and one capacitor (C). When the voltage of INA and INB are approximately the same, the output of MAX903CPA is low level and the capacitor starts to charge through R1 and R2. When the voltage of the capacitor exceeds the threshold voltage, the output of MAX903CPA and NAND gate will be high level and then the capacitor will be discharged. During this process, the charging and discharging time of the capacitor determines the timing period in the circuit.

The MAX903CPA can also be used in temperature control and audio amplifier. In the thermal switch circuit, MAX903CPA compares the temperature sensed by NTC thermistor and preset set point and uses hysteresis to improve the accuracy. In audio amplifier, MAX903CPA is used to control the gain of the amplifier, in which the hysteresis ensures that the amplifier works within a certain linear range.

The MAX903CPA is a five terminal CMOS voltage comparator, which is used in many application fields such as latch circuit and timing circuit. Its working principle is to compare the voltages of INA and INB, and when the difference between them exceeds a certain degree, the output of MAX903CPA will be in high level state. The circuit diagrams connected with the NAND gate and the latch circuit, timing circuit and temperature control circuit are introduced above.

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