LMV321 vs LM321LV: Output voltage range response

ArTzy

Other Parts Discussed in Thread: LM321LV, LMV321, LM321

Hi Experts,

We have this question about the specified output voltage range of the LM321LV series op-amps.

The datasheet states that the output voltage is limited to the positive rail voltage minus 1V. According to fig. 6 this would also apply for the no-load case.

When using this op-amps with 3.3V supply voltage, client noticed that the output has no problems to go all the way up to the positive rail. When they replace it with LMV321 which is R2R specified, there is no difference between the 2.

Why is the output voltage of the LM321LV specified to be limited?

Let us shed light on this together with my client.

Thank you for your support.

Regards,
Archie A.

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 307540 points

The datasheet specifies the V_OH limit for a load of 2 kΩ. There is no guaranteed limit for smaller loads.

Figure 6 appears to be labelled wrong. The functional block diagram shows that the output transistors are rail-to-rail, and figure 4 confirms this.

I'd guess that the output R2R specification was overlooked because it was not needed in a LM321 replacement.

0 ArTzy over 3 years ago in reply to Clemens Ladisch

TI__Genius 16830 points

Thanks Clemens,

What I mean is LMV321 vs LM321LV.

Thank you.

0 Caro Walter over 3 years ago in reply to ArTzy

TI__Mastermind 21102 points

Hey Archie,

These are two different devices, please see the attached comparison table: https://www.ti.com/assets/js/compareParts/compare.html?familyId=1562&parts=LMV321,LM321LV&cols=o1,p3318,p1130,p480,p1261max,p1261min,p78,p23typ,p22typ,p2954,p2max,p1typ,p7typ,p1498,p1192,p3316&lang=en

All the best,
Carolina

0 ArTzy over 3 years ago in reply to Caro Walter

TI__Genius 16830 points

Hi Experts,

Thanks for all of your responses.

I understand the query of my client here and I'm trying to expedite his main concern. I took a snapshot below from LMV321 D/S:

Going back to his main concern, are those highlighted figures inherent with the device? If I understand it correctly, if input signal (either of the two) will go beyond that range (Vn - 0.1) < (Input Signal) < (Vp - 1) , output will go in non-linear region (clipped), correct?

Kindly verify on this.

Thank you!

Regards,
Archie A.

0 ArTzy over 3 years ago in reply to ArTzy

TI__Genius 16830 points

Also, can you confirm if those behavior (snapshot) applicable only for no-load? As per client's report above, they tested it but no clippings happened.

Thank you for your guidance.

+1 Ron Michallick over 3 years ago in reply to ArTzy

TI__Guru**** 159781 points

Archie,

The limit in the data sheet VOH voltage is based on many things. The product name's predecessor "LM321", marketing, test, price, risk and reward.

+1 Clemens Ladisch over 3 years ago in reply to ArTzy

Guru 307540 points

I mentioned the LM321 because the other two devices were designed as low-voltage replacements for it. The LM321 is not R2R, so the other devices do not need to be R2R either.

The LMV321 still has bipolar inputs, but the output uses a MOSFET to allow R2R. (This is an improvement over the LM321.)
The LM321LV is a CMOS device. Both inputs and output are R2R, but the electrical characteristics above V₊ − 1 V are not guaranteed.

+1 Ron Michallick over 3 years ago in reply to Clemens Ladisch

TI__Guru**** 159781 points

Archie,

Clemens Ladisch said:
electrical characteristics above V₊ − 1 V are not guaranteed.

This is the risk; future samples of LM321LV might not have a VOH above V+ -1V.

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LMV321 vs LM321LV: Output voltage range response