TI opamp

Mar 10, 2015 45 Replies
G

Grin.. yeah the beauty and curse of a diode laser. Believe me I know all about this. (A bit ago I spent ~1 week measuring the 25C free running wavelength of 100's of DL's into a wave meter Jr. Whose back reflections is bad too. The back reflection "stair case" has lots of steps in ~1GHz, so ~100MHz. for a ~1m path length. Watching a spectrum seems like a good indicator.

Are back reflections a parametric amplification? So that below some threshold it's "mostly harmless"?

This is much smaller... it smells like a ground loop, shielding thing, which is harder, cause whatever I did ~10 years ago for grounding and shielding was f'ing around till it worked...

George H.

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J

If you arrange the batteries antiparallel, for 0V nom output, the first stage could have a decent gain, 20x at least, and be DC coupled.

Every wire connected to a battery is a thermal antenna + thermocouple. You could get 10s of uV/K from a copper wire soldered to a nickel-over-steel end cap. Millikelvin temp fluctuations could generate some of the noise.

We've seen the same thing in crystal oscillators, in the 1 Hz jitter ballpark. You can really improve a cheap XO's jitter by covering it with foam.

John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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J

I still don't understand. :(

How can fig.27 show the output is zero at 10MHz if the GBW is 110MHz? Should there not be *some* output at 110MHz?

Thank for your help.

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P

There will be, but not much. With a slew rate of 22 V/us, the maximum undistorted sine wave is 22E6/(2 pi * 110E6) = 30 mV peak.

It's intended for audio, where that slew rate is much better than good enough.

Cheers

Phil Hobbs

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J

Thanks, Phil. I think I understand now.

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