Guest Post subject: Quescent current Posted: Sat Sep 24, 2005 12:23
pm I wanna ask a basic question thats bothering me. In many of the
ICs datasheet only the Quiescent current is given.If i have to decide
that what current that IC will draw from battery then should i take
into account only the quiescent current or something else as well ?
Top IR Post subject: Posted: Sun Sep 25, 2005 4:22
am Site Admin Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373 Location: Germany The quiescent current is ususally
the current that the IC draws under no operation. Usually it is the
lowest current. Once the device is doing some activity (Logic activity,
amplification etc) the current consumption grows. When you design
a battery-operated device you should check the quiescent current consumption
when the device is not being operated i.e. at STBY mode and it should
be as low as possible to prolong the battey's life. Usually battery-operated
devices are more in STBY mode than in operation mode so the quiescent
current consumption is the more dominant in terms of battery's life.
_________________ Best regards, - IR Top
danyku Post subject: helloPosted: Sun Sep 25, 2005 11:03
am Lieutenant Joined: Sat Sep 24, 2005 5:34 am Posts:
2 hello IR , its very nice to see somebody from home . today
i discovered this site . i am a FR engineer to . where do you
work ? Top Guest Post subject: Posted: Sun Sep
25, 2005 1:46 pm Well, thanks for the answer IR. So it does mean
that only the Quescent current is important is important when choosing
a battery for MMIC, am i right ? Top IR Post
subject: Posted: Mon Sep 26, 2005 2:29 am Site Admin
Joined: Mon Jun 27, 2005 2:02 pm Posts: 373 Location: Germany
If you design a RF battery-operated circuit, then you should choose
MMICs with low current consumption. The current won't change much when
the MMIC is with or without input signal (It will change I assume by
not more that 10% max. per device). The best thing for RF battery- operated
devices is to do a discrete design (Discrete transistors as amplifiers
or Mixers), or to choose amplifiers with a shut-down option- when the
device is in shut-down it draws the quiescent current. Good
luck! _________________ Best regards, - IR
Top Guest Post subject: Posted: Wed Sep 28, 2005 9:07
am Not neccesarily true. Amplifiers operating in saturation can
operate much higher than the quiescent current easpecially if it is
a class A/B or C amp. You must take this in account when selecting a
battery or you may be dissapointed when you fall short on output power.
Top IR Post subject: Posted: Thu Sep 29, 2005 7:52
am Site Admin Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373 Location: Germany The guest from the previous post
just forgot to mention that you pay in linearity when you operate in
Class A-B or C and your output signal will be distorted (Depends on
the class). So as we all know, efficiency and linearity operate against
each other. You as a designer has to make the right trade-off between
these 2 requirements[/u] _________________ Best regards,
- IR Top Guest Post subject: Posted: Thu
Sep 29, 2005 9:04 am You are correct it most certainly depends on
the linearity requirements. Just wanted to make sure he new the penalty
in case he plans to operate the amp near compression.
Posted 11/12/2012
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