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Wednesday, October 21, 2009

Positive Feedback Circuit Using LM111

This is the circuit that is due to the high gain and wide bandwidth of comparators. This circuit is built by op amps LM111. This is the figure of the circuit.

The trim pins (pins 5 and 6) act as unwanted auxiliary inputs. If these pins are not connected to a trim-pot, they should be shorted together. If they are connected to a trim-pot, a 0.01 mF capacitor C1 between pins 5 and 6 will minimize the susceptibility to AC coupling. A smaller capacitor is used if pin 5 is used for positive feedback. When the signal source is applied through a resistive network, RS, it is usually advantageous to choose an RSÊ of substantially the same value, both for DC and for dynamic (AC) considerations. Carbon, tin-oxide, and metal-film resistors have all been used successfully in comparator input circuitry. Inductive wire wound resistors are not suitable. [Circuit source: National Semiconductor, Inc]

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