From: John Larkin
Subject: Re: 741 question
Date: Sun, 17 Nov 2002 11:04:38 -0800
Organization: Posted via Supernews, http://www.supernews.com
X-Newsreader: Forte Agent 1.91/32.564
On Sun, 17 Nov 2002 09:15:32 GMT, Robert Baer
>> What sort of current consumption can I expect from a 741, configured as a
>> differential temperature switch, running off of a 9volt battery.
>> How long will the battery last in both standby, and when energized, if its
>> output is driving a low-power LED flasher.
>> Is there a lower current consuming equivalent to the 741?.
>> Thanks in advance.
> According to the Fairchild uA741 data sheet issued in April 1969,
>typical supply current is 1.7mA and the maximum supply current is 2.8mA,
>with a +/- 15V supply.
> here is a curve of power dissipation as a function of supply voltage;
>at +/- 5V supply the dissipation is about 5mW for a derived supply
>current of 0.5mA.
> Add to that the load current (from the positive supply in this case).
> There are a lot of micropower opamps that have good drive
>capabilities; look in trade magazines like EE Times or Electronic Buyers
> Manufacturers that come to mind are Linear Technology and National
> You may try their websites using parameter searches, starting with low
>supply current and voltage.
Another gotcha: many opamps (and I think the 741 included) draw extra
current if they are 'railed', which is their normal state if they are
run in open-loop comparator mode.