what is the working of hall effect sensor ??explain the below fig

[swethamenon]

In this fig what are the transistor pairs doing?

 

[jeffrey samuel]

That is a power amplifier that increases the output power of your output signal

 

[FvM]

Assume A is a standard operational amplifier with e.g. 20 mA maximum output current and compensation current Is is is as high as 200 mA. Then you need a current booster stage like the complementary emitter follower shown in the schematic.

 

[swethamenon]

Assume A is a standard operational amplifier with e.g. 20 mA maximum output current and compensation current Is is is as high as 200 mA. Then you need a current booster stage like the complementary emitter follower shown in the schematic.

Is it darlington pair??
how this working here?
power amplifier n emitter follower pair

 

[jeffrey samuel]

Is it darlington pair??
how this working here?
power amplifier n emitter follower pair

It is not a darlington amplifier it is a Class B power amplifier

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They work by stepping up the current of the signal. More like current amplifiers than Voltage amplifiers like CE and other configurations

 

[Tahmid]

It's not a darlington amplifier. It's a push-pull output driver: http://en.wikipedia.org/wiki/Push–pull_output
In certain cases (eg when driving MOSFETs), it's referred to as totem-pole driver.

Darlington transistor/pair: http://en.wikipedia.org/wiki/Darlington_transistor

A simple Google search should clear your doubts on push-pull output driver and darlington pair.

Hope this helps.
Tahmid.