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What is the Difference Between a Line Driver, Open Collector, and Push-Pull Quadrature Encoders and Which One Should I Use?



Hardware: Multifunction DAQ (MIO)

Problem:
I want to use a quadrature encoder with my Multifunction DAQ card. What is the difference between line driver, open collector, and push-pull and which one should I use?

Solution:
Line Driver
A line driver is a sourcing output. When in the on state, a line driver will supply Vcc. In the off state, a line driver will float. Because of this, a sinking input is required for proper operation. Please refer to the table below for a simple example of a line driver.

Open Collector
An open collector is a sinking output. In the on state, an open collector will supply a path to ground. When in the off state, an open collector will float. For proper operation, a sourcing input is required. Please refer to the table below for a simple example of an open collector.

Push-Pull
A push-pull output is a combination of a line driver and an open collector. In the off state it will supply a path to ground and in the on state it will supply Vcc. Please refer to the table below for a simple example of a push-pull output.

Line Driver Open Collector Push-Pull


Which Type of Quadrature Encoder Should I use with my Multifunction DAQ card?
A Push-Pull quadrature encoder is recommended, because the Multifunction DAQ card works best when it is constantly driven. As mentioned above, the Push-Pull configuration does not float, it is always supplying Vcc or ground, which is why it will work best with a Multifunction DAQ card.

Note: To determine the type of quadrature encoder you should use with an Industrial Digital I/O card, please check the user manual for that card.

Related Links:
KnowledgeBase 0FE9BGSR: How Do I Use My Quadrature Encoder with My Data Acquisition Device?
KnowledgeBase 0HFHATRP: Internal Pull-up/Pull-down Resistor Values on the Digital I/O Lines of Data Acquisition Devices

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Report Date: 03/11/2005
Last Updated: 07/22/2015
Document ID: 3JAF2BVB

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