Choose a dual op amp with low offset voltage, small IB and small IQ suitable for smoke detectors.

Hailiang Zhang

Other Parts Discussed in Thread: OPA2344, TLV9002, TLV2432A, TLV2262A, TLV9102, OPA2990, TLV9062

could you help choose a dual op amp with low offset voltage, small IB and small IQ suitable for smoke detectors. Specific requirements are as follows:

Dual op amp, SOIC8 package;
RRIO;
V_offset is less than 1mV, preferably less than 0.5V;
I_B is not more than 200pA, and it is better to be less than 50pA;
The I_Q of each channel does not 200μA;
Support 3V single-ended power supply;
The GBW is not less than 0.5MHz, and 1MHz or more is better.

over 2 years ago

+1 Clemens Ladisch over 2 years ago

Guru 243220 points

Plugging these requirements into the search function does not give many results:
www.ti.com/amplifier-circuit/op-amps/products.html#p480=2;2&p1261min=0.9;3&p23typ=0.5;8000&~p78=In;Out&p2max=0.0015;1&p1typ=0.00032;0.2&p2954=SOIC

The OPA2344 has an offset voltage of 1 mV.

+1 kai klaas69 over 2 years ago

Guru 140200 points

Hi Hailiang,

the OPA2344 is a good candidate. The TLV2432A and the TLV2262A could also be used. And TI recomends the TLV9002 for smoke detectors.

Kai

0 Hailiang Zhang over 2 years ago

TI__Expert 4725 points

Many thanks!

OPA2344 is suitable, but its price is relatively high. 
In addition to TLV9002, I pay attention to TLV342. They have one thing in common. When the common-mode voltage is high, Voffset will deteriorate quickly. If the actual common-mode voltage is low, it can meet the requirements. 
Is my view correct? And how to explain this phenomenon?

0 kai klaas69 over 2 years ago in reply to Hailiang Zhang

Guru 140200 points

Hi Hailiang,

this is explained in section 8.3.2 of datasheet of TLV9002 and is very common for input rail-to-rail OPAmps. In very most cases this is no issue at all.

Kai

0 Caro Walter over 2 years ago in reply to kai klaas69

TI__Genius 17497 points

Hey Hailiang,

Since the target offset voltage is so low (Vos < 1 mV) , I will transfer the thread from general purpose amplifiers to precision op amps.

All the best,
Carolina

0 Caro Walter over 2 years ago in reply to Caro Walter

TI__Genius 17497 points

Hey Hailiang,

The thread has been transferred back to GPAMPS to find a low cost solution. If the Vos specification can be moved to 1.5mV, then there are three options less than $0.50/ku, the TLV9002 (low voltage), TLV9102 (mid voltage), OPA2990 (high voltage). I believe these were being filtered out since Ibias does not have a max spec, the typ spec for all three of these is less than or equal to ±10pA.

All three of these options are provided in SOIC-8, but only the TLV9102 has stock immediately available as of 9/17: 4980 units

Here is the quick search link: www.ti.com/.../products.html

All the best,
Carolina

0 Raymond Zhang1 over 2 years ago in reply to Caro Walter

TI__Mastermind 47796 points

Hi Hailiang,

Adding to the selection list, you may try TLV9062.

If you have additional questions, please let us know.

Best,

Raymond

0 Hailiang Zhang over 2 years ago in reply to Raymond Zhang1

TI__Expert 4725 points

Hi Raymond,

Many thanks!

I noticed that when the bandwidth of some op amps increases, the quiescent current will also increase, and TLV9062 is no exception. Its IQ is relatively large.

0 Hailiang Zhang over 2 years ago in reply to kai klaas69

TI__Expert 4725 points

Hi Kai

Thank you very much!

Regards,

Hailiang

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Choose a dual op amp with low offset voltage, small IB and small IQ suitable for smoke detectors.