IL2901

2011, January, ver.02

APPLICATION NOTE

The IL2901 is high gain, wide bandwidth devices which, like most comparators, can

easily oscillate if the output lead is inadvertently allowed to capacitively couple to the

inputs via stray capacitance. This shows up only during the output voltage transition

intervals as the comparator changes states. Power supply bypassing is not required to

solve this problem. Standard PC board layout is helpful as it reduces stray input-output

coupling. Reducing these input resistors to < 10 k

Ω reduces the feedback signal levels

and finally, adding even a small amount (1 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 pins of any unused comparators should be tied to the negative supply.

The bias network of the IL2901 establishes a drain current which is independent of the

magnitude of the power supply voltage over the range of from 2 VDC to 30 VDC.

It is usually unnecessary to use a bypass capacitor across the power supply line.

The differential input voltage may be larger than V+ without damaging the device.

Protection should be provided to prevent the input voltages from going negative more than

−0.3 VDC (at 25°C). An input clamp diode can be used as shown in the applications

section.

TYPICAL APPLICATIONS (V