John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Had to explain to someone speed/power scales, noise/power does not. We have had requests for 1nV bipolar op-amps that run on 100uA total.

Clarke's 3rd law... :)

Not sure if you're privy to share (and there might be stuff from IEDM, but I've been out of fab for a few years), but has noise/area remained fairly constant as your nodes have shrunk? I would imagine it's improved in terms of active area with process improvements, but not sure if it has scaled similarly.

Obviously Analog Devices is turning out great new low-noise, um, analog devices, :D but is it because more and more of the die is dedicated to the input transistors?
 
Clarke's 3rd law... :)

Not sure if you're privy to share (and there might be stuff from IEDM, but I've been out of fab for a few years), but has noise/area remained fairly constant as your nodes have shrunk? I would imagine it's improved in terms of active area with process improvements, but not sure if it has scaled similarly.

Obviously Analog Devices is turning out great new low-noise, um, analog devices, :D but is it because more and more of the die is dedicated to the input transistors?

Actually the rbb values do scale the re component obviously scales directly only the current densities and heat get in the way. With bi-polars it's mostly old school principles. The end result is that a 1nV transistor is a lot smaller on a modern process.
 
Maybe I did, but buck regulators work on bipolar processes too. My point was that your specified requirement was in uA, not in mW. So if the customer accepts 100uA @ 36V you can use a buck to step that down to 1.2mA @ 3V (efficiency losses not withstanding).

OK I see now, but the request was 100uA at any voltage.
 
Last edited:
You guys are always trying to save a few pennies, while I am trying to get my clients to spring for the more expensive (and better performing) IC or discrete jfets. We live in different worlds.

Right... I had a problem with a guy coming at me for trying to offer a DIY kit cheaper than you could buy the parts yourself, for something that out performs several of Pass's designs at a much lower cost, just because it cost more than a Chinese "version" that can't touch the performance. Could I have made it cheaper in some way? Ya, sure, but why would I want to spend my short time of this planet aspiring for mediocre.
 
An example of cost-no-issue, for hobby of course.

I wanted to use a high voltage BJT from NXP with excellent specs, but only as SOT223.
Rthjc is quite OK, and I wanted to dissipate more heat than would otherwise be possible with the SMD package.
So I figured out a solution to convert it to TO220.
The difficulty is not in the electrical connection, but mechanical integrity.
After all, the hole assembly has to support the weight of any heat sink one might wish to put on.

Don't ask how much it cost. The backing plate was CNC milled copper.
The 0.8mm PCB was not expensive in comparison.


Patrick
 

Attachments

  • 151018 SOT223 2 TO220 Ftr.JPG
    151018 SOT223 2 TO220 Ftr.JPG
    229.2 KB · Views: 189
Status
Not open for further replies.