Let me report what is wirten in the handout:
The circuit furnishes an initial voltage of 2.5 voltes per cell at 25C° to rapidly charge the battery. The charging current decreases as the battery charges. and when the current drops to 180mA, the charging circuit reduces the voltage to 2.35v, leaving the battery in a fully charged state. The LM301 compares the voltage across R1 to 18mv set by R2. The comparators output controls the voltage regulator, forcing it to produce the lower float voltage when the battery charging current drops below 180mA. The 150mV difference between charging and float voltages is set by the ratio of R3 and R4. The LED shows the state of the circuit.
Let's take the case of a 6V battery. To charge that battery, usullay it is suggested to charge it with a Voltage around 7.5V (2.5v per cell as it is mentionned). LM350 or LM317 have a 1.25 voltage reference. So how do we acheive a starting charging voltage of 7.5V from this circuit (When I did my calculation I did not end up with 7.5v but more with Vref=1.25v and Iadj=50uA).
The handout says that "LM301 Compares the voltage across R1 and R2", so the OPAMP here plays a role of a comparator (The output is either High or Low), am I right? In case I am right, how can this OPAMP be Low (sink current to allow the upper LED to be ON ) since its output (PIN 6) is taken form an emitter of a npn transistor (From the datasheet of the LM301).
How does the PNP transistor contribute to the selection of charging voltage (2.5V per cell of 2.35v per cell) ?