I was trying to figure out how IR receivers behave in circuits and came across a type with three leads and a type with two leads. Can someone provide a simple explanation of how these function in a circuit and the difference between them. Is there any difference between these and transistors? Thanks.

To be specific I have some of the three lead ones. The model is TSOP4838.

 

Have you downloaded and read the data sheet on the TSOP4838?

 

some have a bias lead. and some have an internal shield to reduce noisr.

 

The device with two inputs is probably a phototransistor.

The three terminal device includes a system to decode a modulated IR signal (see the datasheet).