OPA827 available

[syn08]

OPA827 is now in production and available for sampling.

http://focus.ti.com/docs/prod/folder...7.html#samples

Give it a shot... this SiGe JFET input opamp is slower than OPA627 but has lower noise, better CMRR and PSRR and lower offset. One to another, and according to my tests, an amazing opamp for audio!

[darkfenriz]

Compared to '627 it doesn't have an input cascode any more, drains directly to vcc. It is amazing it has better PSRR and CMRR for my reasoning.

[syn08]

Originally posted by darkfenriz
Compared to '627 it doesn't have an input cascode any more, drains directly to vcc. It is amazing it has better PSRR and CMRR for my reasoning.

Transistors in SiGe processes have much higher Early voltage compared to the standard silicon counterparts, so no need for cascoding. Also the SiGe material properties are the secret behind the very low noise spec.

[darkfenriz]

Thanks Ovidiu for explaination

There is still something strange for me.
Why distortion for 3V Vout and 20kHz is bigger for G=1 compared to G=11 ?? (figure 3)
Isn't that dynamic common mode distorion?

Regards,
Adam

[jcx]

it would be good to see another decade of frequency - it looks like the G=1 distortion has really taken off above 10 KHz at a much higher rate than the ~ 1 pole response expected from input C modulation interacting with souce/feedback Z imbalance

[Juergen Knoop]

nice specs!
But why should I design with a part I can barely see?
regards

[lineup]

.
OPA827 is a non-complementary input stage and vas.
Followed by a complementary output buffer

The input uses 4 N-JFETs, in differential configuration.
One JFET pair is used to mirror the bias 'tail current' into the input pair.
The emitter current of input pair is fed into emitters of a pair of PNP BJT.
The load is high impedance, another BJT pair at bottom.

Second stage is a standard differential pair of NPN BJT.
The gain is integrated using PNP mirror at top.

Output stage is one standard complementary diamond buffer.
---------------

The new idea, to me, is the input stage arrangement.
It looks good and interesting

This circuit should be very possible to Clone and Explore using SPICE.
We do not know about what is current level in each stage.
But we know typical supply current is 4.8 mA.
Which gives low current in output stage. Low current Class AB.

The output current is 30 mA and short circuit current 65 mA.
The open loop gain is high; x1,000,000 (+120 dB).

For lowest noise using lower input source resistances OPA211 is mentioned as a better choice.

Lineup

[Bonsai]

Pretty straight forward topology. I guess half th e trick in these newer high performance op-amps is in the process - some amazing stuff.

[nelsonvandal]

I expect it to be a double post. When I bought a new computer this old login started to appear.

It simultates excellent.

[AndrewT]

Originally posted by nelsonvandal
I expect it to be a double post. When I bought a new computer this old login started to appear.

It simultates excellent.

do you know who posted that opa829 clone?