Contents
How does a comparator not use hysteresis?
A comparator that does not utilize hysteresis will use a voltage divider to set the voltage threshold. In this case, the comparator compares the input signal (V in) to the threshold voltage (V th ). Then, we apply the comparator’s input signal to the inverting input so that the output will have an inverted polarity.
How is the hysteresis used in a circuit?
The hysteresis will utilize two different threshold voltages (Vth) to prevent the multiple transitions introduced in the circuit. When using hysteresis, the input signal must surpass the VH (upper threshold) to transition low or below the VL (lower threshold) to transition high.
How is hysteresis introduced in a positive feedback resistor?
Hysteresis is introduced as needed via positive-feedback resistor, R4. Hysteresis is applied by feeding back to the positive input a small fraction of the output voltage (which is at an upper or a lower limit). This voltage adds a polarity-sensitive offset to the input, increasing the threshold range.
How does source impedance affect the hysteresis ratio?
If the signal is applied to the non-inverting input, its source impedance should be low enough to have an insignificant effect on either the input scaling or the hysteresis ratio.
How is the threshold voltage of a comparator set?
This configuration uses a voltage divider (Rx and Ry) to set up the threshold voltage. The comparator will compare the input signal (Vin) to the threshold voltage (Vth). The comparator input signal is applied to the inverting input, so the output will have an inverted polarity.
Is the hysteresis range wide enough to reject noise?
Note: Typically, noise is not a factor when using hysteresis, unless it exceeds the hysteresis range. In cases such as this, it would generate additional transitions. Therefore, the hysteresis range must be wide enough to reject the noise in your application.