Why I dont like the NE5534 in PI circuits.

[moodz]

A nice opamp ... except ... it has diodes across the differential inputs .... these go into conduction in typical PI ccts and cause more trouble than you might think. :-)

http://www.geotech1.com/forums/attachment.php?attachmentid=44775&d=1545558659

Even a mouldy old 3130 does not have this ... ( it has zeners ).

http://www.geotech1.com/forums/attachment.php?attachmentid=44776&d=1545558852

Alot of designers dont consider this .... just sayin' :-)

[moodz]

...as we can see from these two shots the fall time for the ne5534 is around 440 ns whilst a non clamping amplifier achieves 10.4 ns and recovers properly ... the ne5534 is still railed after it falls.

lm6171

ne5534

[chemelec]

I have never checked the Waveforms, however I have used the NE5534 Many Times and it Works Good.
However, Looking at the LM6171 Data Sheet, I Might get some Samples and Try it Out.

[waltr]

It is the opamp's recovery time from output over Voltage that seems to be the limiting factor for early first sampling.
The NE5534 does not recovery quickly.

The NE5534 has been chosen for its low noise and speed but this may not have been the best parameters for selection.

I have not yet tried other opamps as the pre-amp on my PI detector. Something else to do as a winter project.
Here is a list of possible op-amps that have been suggested in the forum discussions as fast and low noise for PI pre-amp.

Max410 single

MAX412 dual

AD8055

LT1115

tle2072

OPA627

LM6171

LTC6230

Would also like to hear of others testing different op-amps.

[Tibuck19]

It is the opamp's recovery time from output over Voltage that seems to be the limiting factor for early first sampling.
The NE5534 does not recovery quickly.

The NE5534 has been chosen for its low noise and speed but this may not have been the best parameters for selection.

I have not yet tried other opamps as the pre-amp on my PI detector. Something else to do as a winter project.
Here is a list of possible op-amps that have been suggested in the forum discussions as fast and low noise for PI pre-amp.

Max410 single

MAX412 dual

AD8055

LT1115

tle2072

OPA627

LM6171

LTC6230

Would also like to hear of others testing different op-amps.

I have a few I could test on the surf Pi long board if you guys think it might be worth it

4558D
ba4558
ba4560 which is a Dual high slew rate operational amplifier

I don't think there is anything special about them.

[Carl-NC]

Long ago I switched to the MAX410/412 as my go-to preamp. There are still better choices but only if you are trying to hit cutting-edge performance.

[kt315]

from topic TESORO LOBO AMERICAN DREAM http://www.md4u.ru/viewtopic.php?f=2...t=op27#p156933
easy translation
------
Replacing the op amp in the preamp will in any case require a possible correction of the ferrite phase if the BG adjustment is not enough. When you "calculate" the phase shift, you will not take into account the total, real, phase shift.
The best op amp for preamps is broadband and noise. Among all and sundry the best of the available (by seniority): LT1028, OP27 (37), MC33078, NE5534 (2) Output bias voltages have no decisive role. Only noise that is normalized in the frequency range below 100Hz. Usually normalized for a frequency of 1 kHz. So, it is precisely the precision op amps of the type LT1028, OP27 / 37 that have such an offset of 0 and the noise that is needed. Amplifiers with field inputs do not have these characteristics. Only bipolar input.


OP27 (It’s better not to find this money)
OP37
LT1007
LT1028
Almost all OU work in the pre-amp. Depends on the frequency of the working.

[dbanner]

A lot of speculation, no one here is scientists to get down to the nitty gritty of operational amplifier on the micro level. Our test equipment cannot even begin to measure characteristics on such a level unless you are scientists in university.
Define for me transconductance opamp when speaking of the 3130 and the 3080 and don't forget about the 13700. Everything is a trade off between gain and noise. We of all people should know this.
A much sought after feature of hi fidelity equipment is the ability to faithfully reproduce the original harmonic and melodic subtleties of musical instruments. This was a keen pursuit of engineers of the past with a special relationship to design and function of operational amplifiers.
The secret is not when operating within normal range but rather when operating beyond normal range give op amps there unique character.

[moodz]

swapping the 5534 for a non - crowbar opamp reveals the benefits :-) in a PI frontend

5534 is about 8 microsecond delay with poor rise time and ringing artifacts. ( diode conduction and opamp recovery / slew rate )


LM6171 considerably better.


same circuit ... gain set for 100. Mosfet autoswitch PI front end.