battery powered opamp circuit

[stijn]

Hi all,
I built an EKG amplifier that only exists of an INA121 opamp. I
powered it using 4 9V batteries (2*18V for a LM2940 and LM2990 for
+/-15V.
The problem is, after one days of use the batteries run out of power,
which is just way too soon since the amp is used several days a week.
Are there other ways to get power out of batteries, but that last
longer?
Thx in advance

 

[John Larkin]

On 21 Jan 2004 10:58:18 -0800, stino@biketrials.com (stijn) wrote:

Hi all,
I built an EKG amplifier that only exists of an INA121 opamp. I
powered it using 4 9V batteries (2*18V for a LM2940 and LM2990 for
+/-15V.
The problem is, after one days of use the batteries run out of power,
which is just way too soon since the amp is used several days a week.
Are there other ways to get power out of batteries, but that last
longer?
Thx in advance

Find out where the current is going. The '121 only needs 450 uA
quiescent, so the batteries should last for weeks. Maybe the load is
gobbling current.

You also don't need +-15 volts, and probably don't need regulators
either. Put the batteries in parallel for +-9; that alone will more
than double battery lifetime.

John