Op amp driving LEDs

The LM301 can be used as an open-loop voltage comparator, with its LEDs receiving a total current source of approximately 29mA from the op amp. The input is TTL compatible, and the center of the TTL output transition area is the R1-R2 reference divider that biases the op amp. This circuit has no compensation, and its built-in voltage amplifier stage remains unsaturated due to the clamping of D2 and internal current limiting, so that the circuit achieves the maximum speed of the op amp's open loop.