The article about IR remote control fails to mention that the gain is reduced if the IR receiver receives continuous IR that is modulated at its tuned frequency, so that it ignores the continuous IR modulated at an ultrasonic frequency from compact fluorescent light bulbs. The IR must have bursts of data for the gain to be high. The duration of the bursts is explained in the datasheet.
There are very smart IR receivers that have large amounts of gain and can change the gain so you get a good strong signal all the time. Like in post #2.
The very simplest IR receiver (made of a simple photo transistor or photo diode) have a fixed gain. If the IR drops to 1/2 the output voltage will also drop to 1/2. The output will probably be very small and very dependent on IR signal strength.
Yes there are many different types.
A setup for remote control cars is going to be a lot different from a TV remote control.
What are you looking to do?