Talk:Practical Electronics/Amplifiers

which amplifier is used to amplify the signal in GSM network at the range of 2km.

Asstd
> electronics developers

electronic engineers

> are encouraged to use directly coupled amplifiers whenever possible.

I dont think I've ever been so encouraged. Who is doing this encouraging? How?

> Frequency ranges down to DC are only used when this property is needed.

no, eg there are direct coupled audio amps that go to dc. They rely on the source not containing a dc offset.

> In most cases PCB traces of very closely defined shapes are used instead.

Instead of L&C yes, not instead of trs etc

> Class B amplifiers only amplify half of the input wave cycle. As such they create a large amount of distortion,

both false.

> Class AB is widely considered a good compromise for audio amplifiers, since much of the time the music is quiet enough that the signal stays in the "class A" region, where it is amplified with good fidelity, and by definition if passing out of this region, is large enough that the distortion products typical of class B are relatively small.

This is not how 99% of them work.

> Bipolar transistors are shown, but this design would also be realizable with FETs or valves.

Not valves, significant changes would be needed since they dont come in pnp flavour.

> Most amplifiers use several devices at each stage

amplifier stages almost always use 1 or 2 active devices. 82.31.66.207 (discuss) 00:26, 24 July 2013 (UTC)

Feedback
NFB stabilises gain, reduces distortion & improves frequency response. Its use is widespread.

PFB increases gain, and is primarily used in some rf amplifiers. 82.31.66.207 (discuss) 00:32, 24 July 2013 (UTC)