Three types of the comparator
1. Zero-crossing comparator
When the operational amplifier has no negative feedback branch,it is in the open-loop operation, because the operational amplifier has a large open loop with magnification, as a result, any extremely small input signal will reach the limit output value of the operational amplifier ( slightly less than the supply voltage ) after amplification, so, in open-loop applications, the output of an op amp is usually a rectangular wave. The zero-crossing comparator can realize the comparison of the input signal and the zero potential, which is generally used to detect the zero-crossing point of the AC signal. The signal is transmitted from the inverting terminal of the operational amplifier, and the reference voltage is zero from the same phase terminal.
The zero-crossing comparator has the advantages of simple structure, high sensitivity, and poor anti-jamming capability.
2. The hysteretic comparator has a hysteretic zero-crossing comparator, where the resistance R is connected to the output and the in-phase input, which is the positive feedback, attention should be paid to the difference between negative feedback and negative feedback. In the op-amp circuit, positive feedback is introduced, and the operational amplifier is still in the open loop, and the output is still rectangular, and the edge of the rectangular wave becomes more open-loop than that without positive feedback the op amp is steeper.
3. There is a kind of special comparator integrated circuit in the special comparator market, which has the advantages of small offset voltage, wide range of supply voltage, flexible output potential, etc, widely used, such as LM339, LM393 and so on. The LM339 pin is arranged as shown in figure below. Using the LM339, the output to the positive power supply must be connected with a resistor ( called pull-up resistor ), the size is generally 315kQ. Selecting the pull-up resistor of different resistance will affect the value of the high potential of the output terminal. In addition, the output of each comparator allows the connection to be used together.
If you want to know more, our website has product specifications for the amplifiers, you can go to Allicdata Electronics Limited to get more information.