Programming instructions

Comparator
 National Instruments Corporation 5-9 Multisim Component Reference Guide
5.3 Comparator
A comparator is an IC operational-amplifier whose halves are well balanced and without
hysteresis and is therefore suitable for circuits in which two electrical quantities are
compared. The comparator components may model conversion speed, quantization error,
offset error and output current limitation.
A comparator is a circuit that compares two input voltages and produces an output in either of
two states, indicating the greater than or less than relationship of the inputs.
A comparator switches to one state when the input reaches the upper trigger point. It switches
back to the other state when the input falls below the lower trigger point.
A voltage comparator may be implemented with any op-amp, with consideration for operating
frequencies and slew rate, or with specialized ICs such as the LM339.
The comparator compares a reference voltage, fixed or variable, with an input waveform.
If the input is applied to the non-inverting input and the reference to the inverting input (lower
circuit), the comparator will be operating in the non-inverting mode. In this case, when the
input voltage is equal to (or slightly less than) the reference voltage the output will be at its
lowest limit (near the negative supply) and when the input is equal to (or slightly greater than)
the reference voltage the output will change to its highest value (near the positive supply).
If the inverting and non-inverting terminals are reversed (upper circuit) the comparator will
operate in the inverting mode.
ComponentRef.book Page 9 Thursday, December 7, 2006 10:12 AM