Pyroelectrics are pretty slow and respond to scene changes (or you have to use a chopper); I think there are some platinum silicide sensors that are operable at ambient. Good ~10um sensors are expensive and require cooling for good detectivity. But Stefan-Boltzmann distributions, even though peaking at long wavelengths for chip temperatures, might be amenable to a ratiometric approach (two not-so-long wavelength sensors with a dichroic filter?).
Hmmmmm.
I could probably get my hands on some of our MEMS bolometers, but this sounds like a no commercial potential exercise.
Perfect for Kickstarter! 🙄
An imaging detector would be particularly nice, as one could have a real-time display on the amplifier and watch the various regions of the chips making hazardous excursions toward a hot-spot denouement.
Sheesh. all I wuz tinkin of was a compl pair board
A small "chip on board" with a pair of nicely matched zistors, pins for all leads, an added chip for thermal tracking, and have the whole mounted on one of those clad berquist boards they use for the led's now.
Not for power product, but for the opamp. Make it with hypertronic pins, and it'll be diy useable.
jn
A small "chip on board" with a pair of nicely matched zistors, pins for all leads, an added chip for thermal tracking, and have the whole mounted on one of those clad berquist boards they use for the led's now.
Not for power product, but for the opamp. Make it with hypertronic pins, and it'll be diy useable.
jn
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That is what i would be looking for in bipolar types for my circuit choise; push-pull complimentary, current-mode fb. Didn't someone, once, make a compl type using monolythic process? Who where/are they? -RNM
> The JLH design in #306 is an interesting and useful design, both to talk about, and to upgrade to newer devices.
Thank you John for the info on the input JFETs. Very enlightening.
Would you care to comment on the rest of the topology also ?
Regards,
Patrick
Thank you John for the info on the input JFETs. Very enlightening.
Would you care to comment on the rest of the topology also ?
Regards,
Patrick
As has been mentioned, THAT Corp. makes arrays with complementary devices. I think they are just one chip. In fact they told me that all of the devices are on the chip regardless of the array you get, it's just a matter of what gets hooked up to pins.
EUVL, this topology is similar to other comp-diff topologies, but it is hi Z loaded for highest possible gain. It will be fairly noisy, due to the active loading, and the low Gm input fets. It is a good, linear design, however.
The THAT 300 series are not matched complementary:
THAT Corporation 300-series Low-Noise Matched Transistor Array ICs
Rather, they have either matched NPN or PNP but not both. The hfe's are different between the NPN and PNP, at least.
Close enough. If you are counting on beta matching it's a bad design.
They will sell you chips too, so you could package them yourself (well, via a hybrid circuit subcontractor) and have two quads of devices. And lots of leads 😀
As I mentioned, I asked them why they couldn't get higher beta and they said they had tried but couldn't control breakdown voltages. Much as I appreciate their doing this at all, I roll my eyes a bit at that.
They also worked with Whitlock on his bootstrapped bias instrumentation amp InGenius. Apparently the biggest effort was achieving adequate input protection without too much compromise on the other specs. There are patents but I haven't looked at them. I did notice Rane (?) made a point of referencing prior art when they showed a topology somewhat resembling InGenius (as if to say Don't even think of an infringement lawsuit buddy boy).
John,
That means a passive resistive load would be preferred for low noise design ?
How about the output stage cascode ?
Patrick
That means a passive resistive load would be preferred for low noise design ?
How about the output stage cascode ?
Patrick
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Unfortunately, clearly switching-use characterized. DMOS does not usually have a zero- or negative-tempco of drain current except at impractically high currents, the exception being the ancient parts with rather low transconductance (see the long tangential discussions by tvrgeek in the Sound Quality versus Measurements thread about his mods to a Hafler amp, for example). The positive tempco of the on resistance is mostly irrelevant.
Note that there are no curves showing temperature effects. However they do mention the tempco of gate-source threshold voltage at 1mA as -4.5mV/degree C (about twice as bad as a typical bipolar Vbe). With some devices, the datasheet will show a family of curves and a point where, at three different temperatures, the drain current is about the same. But looking at the power dissipation at that point is discouraging for most devices.
There is also no mention of noise, and MOS is notoriously bad at low frequencies, if better today than years ago. Not recommended for the front end.
Hey, hey a new love is born.
Except that we end up with 16 transistors (when we add an diamond buffer), that's my new favorite. It solves the biasing issues of the VAS when driven by a current source. Nice and new brain food for me, thanks.
IF you want quiet, then resistive loading is the least complex. The second stage cascode seems to just get more gain through raising the output Z.
Time constant close to 10ms for uncooled microbolometer sensors , 7.5-12um spectral range, detector pitch 17-25um. Typical modern dedicated IR camera (sensor, optics, electronics). ~5000-7000 $ 😀
George