Ultra Low Power Op-Amp for 12V Battery, Output to 0V, <100uA Supply Current?

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How can I reduce the quiescent current of a 12V battery-powered relay driver that still needs to pull its output down to 0V?

You cannot get the circuit down to under 100uA just by choosing a different op-amp if the resistor network stays as shown, because the 10k resistor dominates the current draw [#21683142] A low-power candidate mentioned in the thread is the TLC2252CD, which is a rail-to-rail dual op-amp with 35uA supply current, 16V maximum supply voltage, and 50mA output current per channel [#21683137] To reduce total quiescent current, the resistor values need to be increased substantially so they no longer dominate the supply current [#21683142] That change can create bias-current, offset, and temperature-coefficient problems, so the op-amp and resistor values have to be chosen together [#21683142]

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#1 21683133 25 Aug 2019 18:28

Graham Rounce Graham Rounce

Anonymous

Post #1
21683133 25 Aug 2019 18:28

Hello,I'm using an LM324 in a simple circuit to drive a 20mA relay. With no load, it takes 1mA from the 12v supply.As I'll eventually be using batteries, 8 x AA, I'd dearly like this to be a lot less, perhaps under 100uA?
I've browsed around, but the 324 (whose output will go to 0v, which I need) has the lowest supply current I've found.
Anyone more knowledgeable than google ?
Thanks,
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#2 21683134 26 Aug 2019 05:03

Elizabeth Simon Elizabeth Simon

Anonymous

Post #2
21683134 26 Aug 2019 05:03

Graham,For searching on component parameters, I've found Digikey to be better than most.

Elizabeth Simon
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#3 21683135 26 Aug 2019 13:22

Chip Fryer Chip Fryer

Anonymous

Post #3
21683135 26 Aug 2019 13:22

Hi GrahamWithout knowing more about your circuit it is difficult to suggest alternatives. Is it possible for you to explain a bit more the operation?
Regards
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Quiescent current is 1 mA in relay circuit
#4 21683136 26 Aug 2019 21:50

Graham Rounce Graham Rounce

Anonymous

Quiescent current is 1 mA in relay circuit
Post #4 21683136 26 Aug 2019 21:50

Thanks, yes, Digikey does have extensive filtering, but it seems a little too extensive to work very well - at the least, there's a *lot* of tapping/selecting to do! But maybe it's me trying to be too picky.Here's the circuit. The relay triggers, and the motor jolts, when the input goes down. All fine, but the quiescent current is 1mA, much higher than I'd like.Thanks,
Oops, pic in the wrong place again, sorry!
#5 21683137 27 Aug 2019 13:52

Konstantinos Ifantidis Konstantinos Ifantidis

Anonymous

Post #5
21683137 27 Aug 2019 13:52

Hello there!!It's my first post in this forum !
I suggest you to give a look at TLC2252CD. It's a rail-to-rail op amp that has 35uA operating supply current and 16V max supply voltage. It has two channels and each output current per channel is 50mA.
Regards, Kostas.
#6 21683138 27 Aug 2019 13:52

Konstantinos Ifantidis Konstantinos Ifantidis

Anonymous

Post #6
21683138 27 Aug 2019 13:52

Hello there!!It's my first post in this forum !
I suggest you to give a look at TLC2252CD. It's a rail-to-rail op amp that has 35uA operating supply current and 16V max supply voltage. It has two channels and each output current per channel is 50mA.
Regards, Kostas.
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#7 21683139 27 Aug 2019 14:26

lea lovelea lea lovelea

Anonymous

Post #7
21683139 27 Aug 2019 14:26

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#8 21683140 27 Aug 2019 16:17

Leslie Woods Leslie Woods

Anonymous

Post #8
21683140 27 Aug 2019 16:17

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TI low-power op-amp search recommendation
#9 21683141 27 Aug 2019 17:54

Mark Wagner Mark Wagner

Anonymous

TI low-power op-amp search recommendation
Post #9 21683141 27 Aug 2019 17:54

for the lowest power analog devices, I find that Texas Instruments is one of the best right now. You should expect to find Iq < 1uA right now if you look hard enough. Go to their website directly, and search for the operating parameters you need and then see who has it. Octopart will give you a broad view of what distributors have what and they cover Digikey, Mouser and Newark (the 3 I usually buy from for home projects). Good luck!
10 kΩ resistor dominates current draw
#10 21683142 28 Aug 2019 10:42

Richard Gabric Richard Gabric

Anonymous

10 kΩ resistor dominates current draw
Post #10 21683142 28 Aug 2019 10:42

Your current draw is dominated by the 10K resistor if the circuit works as shown, assuming the 0-3V is low impedance, with minor contributions by the other values.If you want a low current op amp, then your resistor values will need to go up in value considerably or they will dominate the current draw. This may create all sorts of problems, including bias current offsets, temperature coefficients, etc, so you can't just blindly choose a very low current op amp without considering all of the input parameters of the op amp, resistors etc,cheers,Richard
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Topic summary

The discussion centers on finding an ultra low power operational amplifier suitable for a 12V battery-powered circuit driving a 20mA relay, with a target supply current under 100µA. The original circuit uses an LM324 op-amp, which draws about 1mA quiescent current, considered too high for battery operation. Suggestions include searching component parameters on distributor sites like Digikey and Octopart for low quiescent current devices. One recommended alternative is the TLC2252CD, a rail-to-rail op-amp with a 35µA supply current and 16V maximum supply voltage, capable of delivering 50mA output current per channel. It is noted that resistor values in the circuit significantly affect current draw, and increasing resistor values to reduce current may introduce offset and temperature coefficient issues. Texas Instruments is highlighted as a leading manufacturer of low power analog devices, with some op-amps offering quiescent currents below 1µA. Overall, careful selection of both the op-amp and supporting passive components is necessary to achieve ultra low power operation.
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Ultra Low Power Op-Amp for 12V Battery, Output to 0V, <100uA Supply Current?

How can I reduce the quiescent current of a 12V battery-powered relay driver that still needs to pull its output down to 0V?

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