Simulating opamps for Rail to Rail output RRO

[lineup]

Simulation of many opamps to see what is the dropout voltage.
The load is around 5mA peak. Voltage is when THD is still <0.0005%
Supply voltage +/-18 Volt.
Disclaimer: It all comes down to how good the SPICE models are.

Dropout Voltage, Opamp

RRO OPamps with low dropout
0.13 OPA210
0.16 OPA2156
0.17 OPA172
0.17 OPA1688
0.20 OPA145
0.20 OPA1655
0.22 OPA182
0.22 OPA140
0.23 OPA192
0.23 OPA211
0.25 OPA189
0.36 OPA1641
0.38 OPA197
0.47 OPA1611

Not RRO but with low dropout
0.74 OPA132
0.74 OPA134
1.00 OPA828
1.08 LM4562
1.14 LME49710
1.20 OPA1677
1.30 OPA228

Not RRO with more dropout
1.81 AD847
1.81 AD797
1.83 AD825
1.94 AD8021
2.14 OPA637
2.16 OPA627
2.20 TL051
2.30 NE5534
2.50 OPA604

Not RRO and very high dropout
4.75 TL071
4.77 AD846

 

[stv]

Some (most?) of them are probably asymmetric regarding positive and negative dropout voltage.

 

[jan.didden]

How do these values compare to the datasheet values?

Jan

 

[rsavas]

I think member lineup puts way to much faith in opamp spice models.
We had this discussion on thd measurements he agreed that the numbers are basically bogus but still tries to use them as being accurate, which is not the case imo and misleading members in his numbers.

 

[rayma]

It's easier to just test them operationally on a breadboard for the actual values,
as well as being much more accurate.

 

[lineup]

This is a new test.
Dropout voltage at 10mA.

RRO OPamps Dropout at 10mA
0.22 OPA210
0.24 OPA140
0.26 OPA2156
0.26 OPA211
0.29 OPA145
0.31 OPA1688
0.32 OPA172
0.35 OPA1655
0.35 OPA1641
0.41 OPA182
0.43 OPA192
0.45 OPA189
0.51 OPA197
0.73 OPA1611

Not RRO Opamps at 10mA
0.75 OPA134
0.75 OPA132
1.03 OPA828
1.12 AD846
1.17 LM4562
1.24 LME49710
1.30 OPA228
1.51 OPA1677

Not RRO Opamps at 10mA
1.81 TL051
1.88 AD825
1.90 AD797
2.04 AD847
2.14 OPA637
2.15 OPA627
2.23 NE5534
2.31 AD2021
2.46 OPA604
2.50 TL071

 

[stv]

Voltage is when THD is still <0.0005%

What gain did you use?

 

[WhiteDragon]

I think member lineup puts way to much faith in opamp spice models.
We had this discussion on thd measurements he agreed that the numbers are basically bogus but still tries to use them as being accurate, which is not the case imo and misleading members in his numbers.

For the most part somewhat agree.

TI will state well what has been modeled.
In more advanced macros.
When it comes to Input noise figures, DC offset, temperature drift, bandwidth, open loop behavior
Output stage behavior, If power rail includes current, protection, clamps, temp shutoff Etc Etc

Why I used TI software and included TI models , macros.
Far as basic stuff like Stability, DC offset and even Noise , THD
Especially very high frequency models. And models including
protection etc etc. The models are very accurate and more than
good enough to have expected results. Specially DC offset
and even getting high frequency models to be stable in specific
conditions/loads. Extremely useful and accurate.
Even protection circuits, clamps, temp cutoff current limit.
Will hit stated thresholds according to data sheet.

Far as THD even a simple TL072 in a realistic model wont exceed
.003 % distortion and wont give misleading figures if the modeling program
is used correctly.

And when comparing higher performance models.
Matching stated data sheet conditions. THD is often close
if not the same to datasheet.

So agree models will always be judged. But as far as expected
output voltages into expected loads and using voltage sources
with internal resistance in the model. TI does a very good job
suppling realistic models. And dont have to fool around with
software errors/downloads and importing issues. Since the TI
software includes all the models.

Far as OP data. Under similar model conditions.
If OPA210 shows .22 and TL071 shows 2.50
They aint blowing unrealistic smoke up our butts.
Even without testing and just basic understanding of opamp
behavior and topologies. Would be realistic enough
to not have false expectations.

TI has numerous demos of TINA comparing models and real
world accuracy of measurements. And is a very big part
of the full lab system and free version. Is assuring accuracy,
and more advanced macros state well what they do model
with high accuracy.

 

[TNT]

This is a new test.

IRL or simulation?

//

 

[tomchr]

+1 for real or simulated?

Often THD is not included in the simulation models. If it is, it may not be accurately modelled.

The test results are relevant ... if they're valid.

Tom

 

[EUVL]

Please kindly change your title to
Simulating opamps for Rail to Rail output RRO
just to avoid confusing other forum members.


Thanks, Patrick

 

[lineup]

Simulating opamps for Rail to Rail output RRO.
Is the very correct title ...

 

[rayma]

Thread title changed.

 

[Mooly]

+1 for real or simulated?

+2 when it comes to opamps the models can be dire.

I remembered this from ages ago. Wonder if they are still the same in the latest LTspice versions.

https://www.diyaudio.com/community/...ack-opamps-in-simulation-and-practice.243476/

 

[lineup]

There are more or less good models
but there are plenty of inaccurate models floating around.
Yes, one should not be fooled by SPICE. It is easy to be.