Ok,
If you were to tie 7 volts to the Emitter of a PNP transistor,
Connect a load, say a lamp, to the Base of that transistor, and the other side of the lamp to the GND,
The voltage the lamp connected to the Base will be getting 6.3v, that is the internal switch on voltage of the Base, IE, the 1 diode voltage drop. The lamp will receive 6.3v instead of 7v, but, it will always stay on.
Now, when I say that you shouldn't go above 300ma, IE, a strong lamp, you will burn out the transistor, both in heat and Base-Emitter junction.
If you don't connect anything to the Base, the Collector (current sense output) is freely pulled down to GND by the 10k resistor in my design, but, if you connect the lamp to the Base, this pulling down on the base turns on the transistor and pulls the output Collector to the 7v connected to the Emitter. This is your load sense output. With a connected load/lamp, the base is turned on and the Emitter goes high. (If you run this at 7v, then the high output will be 7v. If you are feeding a logic level MCU, a series resistor may be used is the MCU input has diode clamps, or, 2 resistors on the output using the center tap will divide the output voltage to a safe level in place of the 10k.)
You should be able to try this out with a 2N3906, however, with that transistor, make sure your load, IE lamp doesn't go above 50ma, or the transistor will blow.
Once you are comfortable with this, we can take a look at adding either a power diode or just a beefier transistor if you need to support loads of 1 or more amps.
There is no comparator in this design. The transistor is your comparator...