TI continues to surprise us with top notch products. After the OPA1656 I 'discovered' the OPA1637. A fully differential amplifier with excellent audio specs.
Ordered the eval module to get a head start*. I can see several places where this would fit very well, like fully balanced post-DAC filtering and/or I/V conversion, fully balanced preamps, fully balanced active filters/xovers. And, my own target, an improved fully balanced AutoRanger.
Anybody here with similar ideas?
Jan
*If the international shipping system holds up, hopefully.
Ordered the eval module to get a head start*. I can see several places where this would fit very well, like fully balanced post-DAC filtering and/or I/V conversion, fully balanced preamps, fully balanced active filters/xovers. And, my own target, an improved fully balanced AutoRanger.
Anybody here with similar ideas?
Jan
*If the international shipping system holds up, hopefully.
The datasheet looks good, the inputs seem truly symmetrical. All too often differential amplifiers have very poor AC common mode rejection.
Your post reminds me, I want to build a decent connector board to bypass my PCs horrible 3.5mm jacks
Your post reminds me, I want to build a decent connector board to bypass my PCs horrible 3.5mm jacks
It would be a nice project to base a phono preamp on it. I've seen some (discrete) fully balanced designs here and they were generally well regarded.
Hans Polak did one, there's a tread about it.
Jan
Hans Polak did one, there's a tread about it.
Jan
Same pinout as OPA1632, it seems, but a less hot input stage with added input bias current cancellation (no biggie in a true balanced application). This part would be intended for more normal surrounding impedances. You could use it in a fully balanced phono preamp, I guess, but the duplicated RIAA network in these is always a nuisance.
We're not exactly drowning in these fully-differential parts, so any new type is welcome I guess.
BTW, I never noticed that OPA1632 specs do not really add up. 2 µA of input bias current (typ) but only 0.4 pA/√(Hz) of input current noise? You'd get 0.8 from shot noise alone. (Besides, even the lowest-noise bipolar opamps do not manage en * in substantially below 1. OPA1632 specs would indicate 0.6!) OPA1637 specs look way more realistic.
We're not exactly drowning in these fully-differential parts, so any new type is welcome I guess.
BTW, I never noticed that OPA1632 specs do not really add up. 2 µA of input bias current (typ) but only 0.4 pA/√(Hz) of input current noise? You'd get 0.8 from shot noise alone. (Besides, even the lowest-noise bipolar opamps do not manage en * in substantially below 1. OPA1632 specs would indicate 0.6!) OPA1637 specs look way more realistic.
Fully agree on the 'more normal impedances' in the fb networks.
I'm still waiting for my eval board ... :-(
Fedex says 27 April, but you never know in these interesting times.
Jan
I'm still waiting for my eval board ... :-(
Fedex says 27 April, but you never know in these interesting times.
Jan
Last edited:
I've got an MM phono waiting for test with the OPA1632. TI website not working for me at the moment so cannot see how the specs compare.
Got some time to check out the OPA1637 EVM. Some EVMs have 0 ohm output isolation resistors in R4, R7 positions. The latest units will have small non-zero resistors there to guarantee stability with cap loads. In case you do see oscillations, check that these resistors are non-zero.
But, with that, the performance is absolutely stellar, see attached. Measured via a balanced twin-tee, down in the AP noise floor ...
And this is with a gain of 5, so for unity gain expect at least 10dB lower yet!
Jan
But, with that, the performance is absolutely stellar, see attached. Measured via a balanced twin-tee, down in the AP noise floor ...
And this is with a gain of 5, so for unity gain expect at least 10dB lower yet!
Jan
Attachments
Last edited:
That THP210 is typically meant for battery/low power systems. The supply current is just 0.95mA, but the trade-offs are also visible: GBW less than 10MHz, slew rate 'just' 15V/uS.
So these are two different products, for different target applications. But it may be a nice candidate for a differential servo ;-) .
Jan
So these are two different products, for different target applications. But it may be a nice candidate for a differential servo ;-) .
Jan
So ?
How does it compare to the OPA1632 ?
Is it meant to replace it or...?
I must confess I'm confused with TI's nomenclature and op-amp marketing... EDIT : even more so when it seems THP210 is the SAME part but with better input offset voltage ? Because it's not a "Burr-Brown Audio" part but sorted in the Precision Op-amps range ?
How does it compare to the OPA1632 ?
Is it meant to replace it or...?
I must confess I'm confused with TI's nomenclature and op-amp marketing... EDIT : even more so when it seems THP210 is the SAME part but with better input offset voltage ? Because it's not a "Burr-Brown Audio" part but sorted in the Precision Op-amps range ?
Last edited:
More likely to be an extra trimming process step rather than sorting
The TI factory in Kuala Lumpur is enormous
The TI factory in Kuala Lumpur is enormous
Yes, THP210 is said to be laser trimmed if you look in the documentation.
So, is it an improvement over the 1632 ?
So, is it an improvement over the 1632 ?
Last edited:
I have not used it yet, but yes. Here is the PSpice model for the OPA1637: https://www.ti.com/lit/zip/sbombf8
There is also one for the THP210, as well as TinaTI and other versions.
There is also one for the THP210, as well as TinaTI and other versions.