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university:courses:electronics:electronics-lab-opamp-comparator [16 Feb 2020 21:14] – [The op-amp as a "comparator":] Doug Mercer | university:courses:electronics:electronics-lab-opamp-comparator [16 Feb 2020 21:17] – [The op-amp as a "comparator":] Doug Mercer | ||
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- | Op Amps and comparators may seem interchangeable at first glance based on their symbols and pinouts. The Analog Parts Kits is supplied with a variety of op-amps and the AD8561 high speed voltage comparator that was used in the earlier | + | Op Amps and comparators may seem interchangeable at first glance based of their symbols and pinouts. The Analog Parts Kits is supplied with a variety of op-amps and the AD8561 high speed voltage comparator that was used in other activities. Some designers might be tempted to use or substitute readily available op amps as voltage comparators in their projects. There are very important differences however. Comparators are designed to work without negative feedback or open-loop, they are generally designed to drive digital logic circuits from their outputs, and they are designed to work at high speed with minimal instability. Op amps are not generally designed for use as comparators, |
<note important> | <note important> | ||
- | Yet many designers still try to use op amps as comparators. While this may work at low speeds and low resolutions, | + | Yet many designers still try to use op amps as comparators. While this may work in some cases at low speeds and low resolutions, |
The most common issues are speed (as we have already mentioned), the effects of input structures (protection diodes, phase inversion in FET amplifiers such as the ADTL082, and many others), output structures which are not intended to drive logic, hysteresis and stability, and common-mode effects. | The most common issues are speed (as we have already mentioned), the effects of input structures (protection diodes, phase inversion in FET amplifiers such as the ADTL082, and many others), output structures which are not intended to drive logic, hysteresis and stability, and common-mode effects. |