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Design >> RF Design >> Limiting amplifier
https://designers-guide.org/forum/YaBB.pl?num=1321192818

Message started by henrytqy on Nov 13^th, 2011, 6:00am

Title: Limiting amplifier
Post by henrytqy on Nov 13^th, 2011, 6:00am

Hi dear all,

Recently I read some papers about limiting amplifer, but I'am not fully understand it. In RF design we often heard about PA,mixer,LNA. Why do we seldom heard of LA?

Can someone explain what's the limiting amplifier used for in the RF circuit? In what situation that we need it?

Thanks lot~~

Title: Re: Limiting amplifier
Post by raja.cedt on Nov 13^th, 2011, 6:21am

hello,
there is no speciality about limiting amplifier(LA)..it's normal amplifier (with out any gain control to prevent saturation fro large signals) which is generally operate in small signal input regime. In general you will find LA in the baseband to amplify the week signal. There is another amplifer called AGC which is also LA with soma gain control mechanism to avoid saturation by redusing the gain in the presence of large signal.

Hope this helps.

Thanks,
raj.

Title: Re: Limiting amplifier
Post by aaron_do on Nov 13^th, 2011, 5:11pm

Hi,

limiting amplifiers can be used in baseband as raja.cedt pointed out. They are useful for constant envelope modulated signals in that they can amplify your signal up to a specified amplitude like in an AGC, but much faster since there is no loop. So in other words they are immune to sudden changes in the signal amplitude.

regards,
Aaron

Title: Re: Limiting amplifier
Post by loose-electron on Nov 14^th, 2011, 10:03am

Limiting amplifiers - two classes of these that I know of -

Amplifiers that are design to reduce gain as input signals get larger coming in. (as mentioned here)

Amplifiers with a fixed gain, used in cascade within a log-amp structure.