LP239 Datasheet, PDF (5/7 Pages) Texas Instruments – LOW-POWER QUAD DIFFERENTIAL COMPARATORS

LP239, LP339, LP2901
LOW-POWER QUAD DIFFERENTIAL COMPARATORS
SLCS004A – OCTOBER 1987 – REVISED MAY 1988
APPLICATION INFORMATION
Without transistor Q3, if the output voltage were allowed to drop below 0.8 V, transistor Q1 would saturate and
the output current would drop to zero. The circuit would be unable to pull low current loads down to ground or
the negative supply, if used. Transistor Q3 has been included to bypass transistor Q1 under these conditions
and apply the current I1 directly to the base of Q2. The output sink current is now approximately I1 times the
h_FE of Q2 (700 µA at V_O = 0.4 V). The output of the devices exhibit a bimodal characteristic with a smooth
transition between modes.
In both cases, the output is an uncommitted collector. Several outputs can be tied together to provide a dot logic
function. An output pullup resistor can be connected to any available power supply voltage within the permitted
power supply range, and there is no restriction on this voltage based on the magnitude of the voltage that is
supplied to V_CC of the package.
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