Quad General Purpose Differential Comparator - LM339
An application from an old TI datasheet showing the versatility of this comparator. For me it was a workhorse and like LM324 was used in many products.

Current drain is independent of the supply voltage. The outputs can be connected to other open-collector outputs to achieve wired-AND relationships.
Differential to TTL convertor using LM339
- Single Supply or Dual Supplies
- Wide Range of Supply Voltage:
- Low Supply-Current Drain Independent of Supply Voltage... 0.8 mA Typ
- Low Input Bias Current ...25 nA Typ
- Low Input Offset Voltage . . . 2 mV Typ
- Common-Mode Input Voltage Range Includes Ground
- Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . ±36 V
- Low Output Saturation Voltage
- Output Compatible With TTL, MOS, and CMOS