confused with phototransistor and TSOP .... help me plz!

hi......!
i am a beginner plz help me to get rid of my confusion.
i wanted to create a line follower obstacle detection and photo phobe and etc..
i generally know about LDR and photo diode but while searching for line follower circuits read about many circuits and got confused about what i know before also.
1)what is photo transistor?is it not the photo diode?what is the difference between them?does it also have rx and tx pair or only a single one?

2)what is TSOP 1738 what for it used for ?is it not same as photo diode?
how is it different from photo diode?does it also have emitter and receiver modules?are there different varieties of tsop available?


please explain me case wise.
thankq..

Hi

Internally a phototransistor is very different compared to a photodiode. However, externally they appear very similar.

In a photodiode the inverse leaking current depends on the amount of light.

In a photo transistor the light is like the base current. The collector-emitor current is an amplified version of the base current induced by the light. A photodiode is therefor more sensitive then the Photodiode.

In this tutorial a photo transistor is used to measure light with a phototransistor:
**broken link removed**

Slorn
--
Dwengo... gets you started with microcontrollers!

A photo-diode can be used two ways;
1) It leaks a small current when it has a reverse bias voltage and light.
2) It is a small solar cell that produces a small current when it has light.

A photo-transistor leaks current like a photo-diode when its collector has a voltage and has light but the transistor has gain so it is more sensitive than a photo-diode.

An LDR is a light sensitive resistor that responds slowly.