Application Hints

The LM193 series are 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

change 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 the input re-

Ω reduces the feedback signal levels and

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 LM193 series establishes a drain

current which is independent of the magnitude of the power

supply voltage over the range of from 2.0 V

It is usually unnecessary to use a bypass capacitor across

the power supply line.

The differential input voltage may be larger than V

damaging the device (Note 8). Protection should be provided

to prevent the input voltages from going negative more than

−0.3 V

shown in the applications section.

The output of the LM193 series 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 permitted supply voltage

range and there is no restriction on this voltage due to the

magnitude of the voltage which is applied to the V

of the LM193 package. The output can also be used as a

simple SPST switch to ground (when a pull-up resistor is not

used). The amount of current which the output device can

sink is limited by the drive available (which is independent of

V

β of this device. When the 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 ap-

proximately 60

Ω r

voltage of the output transistor (1.0mV) allows the output to

clamp essentially to ground level for small load currents.

Basic Comparator

Driving CMOS

Driving TTL

00570935

00570936

00570937

Squarewave Oscillator

Pulse Generator

Crystal Controlled Oscillator

00570938

00570939

* For large ratios of R1/R2,

D1 can be omitted.

00570940

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