Quescent Current - RF Cafe Forums
Post subject: Quescent current Posted: Sat Sep 24, 2005
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 ?
Post subject: Posted:
Sun Sep 25, 2005 4:22 am
Jun 27, 2005 2:02 pm
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
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.
Post subject: helloPosted: Sun Sep 25, 2005 11:03
Joined: Sat Sep 24, 2005 5:34 am
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 ?
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 ?
Post subject: Posted: Mon Sep 26, 2005
Joined: Mon Jun 27, 2005 2:02
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.
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.
Post subject: Posted: Thu Sep 29, 2005 7:52 am
Joined: Mon Jun 27, 2005 2:02 pm
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]
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.