LM2901/ LM2901A/ LM2903/ LM2903A

Document number: DS36779 Rev. 3 - 2

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May 2016

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LM2901/ LM2901A/ LM2903/ LM2903A

Application Information

General Information

The LM2901/2903 series comparators are high-gain, wide bandwidth devices. Like most comparators, the series can easily oscillate if the output

lead is inadvertently allowed to capacitive couple to the inputs via stray capacitance. This shows up only during the output voltage transition

intervals as the comparators change states. Standard PC board layout is helpful as it reduces stray input-output coupling. Reducing the input

resistors to <10k

Ω reduces the feedback signal levels. Finally, adding even a small amount (1.0 to 10 mV) of positive feedback (hysteresis) causes

such a rapid transition that oscillations, due to stray feedback, are not possible. Simply socketing the IC and attaching resistors to the pins will

cause input-output oscillations during the small transition intervals unless hysteresis is used. If the input signal is a pulse waveform, with relatively

fast rise and fall times, hysteresis is not required. All input pins of any unused comparators should be tied to the negative supply.

The bias network of the LM2901/2903 series comparators establishes a quiescent current independent of the magnitude of the power supply

The output of the LM2901/2903 series comparators is the uncommitted collector of a grounded-emitter NPN output transistor. Many collectors can

be tied together to provide an output OR’ing function. An output pull-up resistor can be connected to any available power supply voltage within the

LM2901/2903 series comparator package. The output can also be used as a simple SPST switch to ground (when a pull-up resistor is not used).

maximum current limit is reached (approximately 16mA), the output transistor will come out of saturation and the output voltage will rise very

rapidly. The output saturation voltage is limited by the approximately 60

transistor (1.0mV) allows the output to clamp essentially to ground level for small load currents.