Hi Lineup,
A minor point: I think it was TI that took over BB.
The OP27/37 were further developments of the OP07 IIRC, they were improved in DC offset and drift. The OP27/37generally are not so hot as to bandwidth and distortion.
If you use them in audio you may be totally satisfied, but if you look at the specs there are (much) better ones. For a price, indeed.
Jan Didden
A minor point: I think it was TI that took over BB.
The OP27/37 were further developments of the OP07 IIRC, they were improved in DC offset and drift. The OP27/37generally are not so hot as to bandwidth and distortion.
If you use them in audio you may be totally satisfied, but if you look at the specs there are (much) better ones. For a price, indeed.
Jan Didden
thanks for correcting me.
i got it wrong
because the actual datasheet i have in my PC and was looking at
is a Analog Devices, AD, pdf
links:
Texas: http://www.ti.com/
Burr-Brown: http://www.burr-brown.com/
This doesnt change the fact that OP37 is
a very good OP-Amp for audio at its price.
And I am at www.diyaudio.com right now.
Also true that, if you are willing to pay and can do this,
there are numerous of OP-amps with better specs.
This, however, does not always mean they would do better in audio.
I have seen people here at forum, suggesting newly released op-amps
with enormous specs regarding bandwidth and other data.
But trying to use them for audio, will get you into troubles,
if not by bad sound, so with very great risk of instability
and extreme needs for special circuit board layout and decoupling.
But your remark is quite accurate - it is the truth!
i got it wrong
because the actual datasheet i have in my PC and was looking at
is a Analog Devices, AD, pdf
links:
Texas: http://www.ti.com/
Burr-Brown: http://www.burr-brown.com/
This doesnt change the fact that OP37 is
a very good OP-Amp for audio at its price.
And I am at www.diyaudio.com right now.
Also true that, if you are willing to pay and can do this,
there are numerous of OP-amps with better specs.
This, however, does not always mean they would do better in audio.
I have seen people here at forum, suggesting newly released op-amps
with enormous specs regarding bandwidth and other data.
But trying to use them for audio, will get you into troubles,
if not by bad sound, so with very great risk of instability
and extreme needs for special circuit board layout and decoupling.
But your remark is quite accurate - it is the truth!
lineup said:
Well, to this I respectfully disagree. This is an opamp optimised for DC and low frequency. They wisely don't even publish distortion curves in the data sheet.
Even at the low price, there are better opamps for audio. The OP27/37 is NOT a very good opamp for audio, even at its price.
Jan Didden
I love the OP27/37 for the fact that they are both very low DC offset and also have excellent slew rate and bandwidth to boot.
They are indeed very flexible analogue instrumentation amplifiers.
I use these op amps when building AF test instrumentation that requires both high frequency performance and low DC offset.
I have a reserve stash of OP27s, OP37s and LM627s that I reserve for these purposes.
If any one knows of an op amp that can out do the OP27 and OP37 in both DC offset/bias and Slew rate/Bandwidth I am very interested!
They are indeed very flexible analogue instrumentation amplifiers.
I use these op amps when building AF test instrumentation that requires both high frequency performance and low DC offset.
I have a reserve stash of OP27s, OP37s and LM627s that I reserve for these purposes.
If any one knows of an op amp that can out do the OP27 and OP37 in both DC offset/bias and Slew rate/Bandwidth I am very interested!
Hi,
I have not compared specs, but the 227 and 228 may get close or even better in a few respects.
Where the 228 is good is audio.
I have not compared specs, but the 227 and 228 may get close or even better in a few respects.
Where the 228 is good is audio.
I have been doing a bunch of small cmoy amps this last two weeks, and experimented with both opa2132, opa2134, and OPA134. (lol, and lm385 while I waited for chips)
In my opinion there is no reason to settle for the dual 2134, its still ok in single versions like the 134, with noise offset pins, but the price diffirence is so small and quality jump is so big from 2134 to 2132 .
I found the opa134 quite consistently produced inside the 4mv of offset voltage that one can adjust back to 0.
In my opinion there is no reason to settle for the dual 2134, its still ok in single versions like the 134, with noise offset pins, but the price diffirence is so small and quality jump is so big from 2134 to 2132 .
I found the opa134 quite consistently produced inside the 4mv of offset voltage that one can adjust back to 0.
filgor said:
Specifications OP27
-3dB Bandwidth 8MHz
Slew Rate 2.8V/µs
Input Noise (nV/rtHz) 3.2nV/rtHz
You got to be kidding! Or maybe you're just having fun...😉
Jan Didden
Janneman, you are quit clever with these things if I remember correctly. I have a datasheet question.
One of the specs is; FET INPUT: IB = 50pA max
Does this mean that the most current I can present to the input is 50 ten thousands of an amp?
i.e 1V over 2Kohm = 0.0005A
One of the specs is; FET INPUT: IB = 50pA max
Does this mean that the most current I can present to the input is 50 ten thousands of an amp?
i.e 1V over 2Kohm = 0.0005A
Hi Nordic,
the bias current is the current the input needs to operate correctly. Depending on whether it is Pch or Nch will determine if the bias current sinks or sources to ground.
It has little to do with input current from a signal source.
50pA are 50A*10^-12=50uA*10^-6=0.000,000,000,05A I have put some comma separators in, to let you count the zeros more easily.
If an input impedance setting resistor (try 100k) were placed from input to ground and this 50pA of bias current flowed through it then the input would sit at 50*10^-12 * 100*10^3=5uV away from zero volts.
the bias current is the current the input needs to operate correctly. Depending on whether it is Pch or Nch will determine if the bias current sinks or sources to ground.
It has little to do with input current from a signal source.
50pA are 50A*10^-12=50uA*10^-6=0.000,000,000,05A I have put some comma separators in, to let you count the zeros more easily.
If an input impedance setting resistor (try 100k) were placed from input to ground and this 50pA of bias current flowed through it then the input would sit at 50*10^-12 * 100*10^3=5uV away from zero volts.
Could Oscon caps be the reason my little opa134 boards go into oscilation after abouit 2 minutes... they play beautifuly then suddenly the sound goes all distorted, switch em on and off and the will play again for a few seconds...
Want to climb the wall... so wish I had a scope.
Want to climb the wall... so wish I had a scope.
Hi,
is there a clue in the sudden change.
Temperature induced instability?
or
Is something detecting over temp and shutting down?
is there a clue in the sudden change.
Temperature induced instability?
or
Is something detecting over temp and shutting down?
Nope, not feeling any heat, its only running off a 9v cell which I split in two rails and ground with 4k7 resistors.. the datasheet calls for 10nf bypass caps I have used some 100nf ones as I have to wait till tommorrow for the smaller ones to come from Johannesburg. Surely that won't cause it...
Nordic said:
Those batteries may drop slowly after turn-on. After some turn-off time they partially recover. Try with fresh batteries.
Jan Didden
Nordic said:
Does it work longer with a _fresh_ battery?
Try connecting a large electrolytic across the battery.
2200 uF and up. See what happens.
regards, Gerhard
Ok, I put the battery in the charger overnight, will test in the morning...According to my calculations the 4k7 rail splitter resistors may be a bit high concidering that I have 2 opamps connected to the same battery.
If I drop em to 2k2 it should give me about 20ma per rail on a fresh charge, right? Would this be enough for two opa134s?
If I drop em to 2k2 it should give me about 20ma per rail on a fresh charge, right? Would this be enough for two opa134s?
mudihan said:
I measured few op27's some time ago, AD-version was worst of them and maxim's op27 was best (thd, 1khz) there was also third manufacturer which name i cant remember..
btw. MAX427 is way better than any op27 in thd-tests...
Hi,
The quiescent of two 134s is about 10mA. Add in the peak output current and you are way over the spare 10mA you have allowed for. Remember the output current is the resistive load//feedback load//output capacitance. If your output load is 5k, it is very misleading to assume your output current is output voltage/5k.
no.
The quiescent of two 134s is about 10mA. Add in the peak output current and you are way over the spare 10mA you have allowed for. Remember the output current is the resistive load//feedback load//output capacitance. If your output load is 5k, it is very misleading to assume your output current is output voltage/5k.
Thanks, will bump total supply to 80mA, still got to wait a few hours for the cell to finnish chargeing...
about the op27.. saw the following in the opa134 datasheet...
"With low source impedance, the current noise term is
insignificant and voltage noise dominates the noise performance.
At high source impedance, the current noise term
becomes the dominant contributor.
Low noise bipolar op amps such as the OPA27 and OPA37
provide very low voltage noise at the expense of a higher
current noise. However, OPA134 series op amps are unique
in providing very low voltage noise and very low current
noise."
about the op27.. saw the following in the opa134 datasheet...
"With low source impedance, the current noise term is
insignificant and voltage noise dominates the noise performance.
At high source impedance, the current noise term
becomes the dominant contributor.
Low noise bipolar op amps such as the OPA27 and OPA37
provide very low voltage noise at the expense of a higher
current noise. However, OPA134 series op amps are unique
in providing very low voltage noise and very low current
noise."