Re: tanh stuff
You should be able to re-optimise at 47C and give some variable a simple TC to get a first order compensation. PTAT currents are easy to make (a 1.25V reference impressed on a degenerated transistor is very close).
This would couple BTW to that differential VAS with no further major distortions, a PIM free op-amp.
Edmond Stuart said:
You should be able to re-optimise at 47C and give some variable a simple TC to get a first order compensation. PTAT currents are easy to make (a 1.25V reference impressed on a degenerated transistor is very close).
This would couple BTW to that differential VAS with no further major distortions, a PIM free op-amp.
Edmond,
I don't see how that circuit can work. I agree with Bear, I just see the output connected to two current sources between the rails. Or are the current sources a function of the strange looking rectangular bar with a + next to the top of it. This is beyond what I'm familiar with, could you explain the current sources?
I don't see how that circuit can work. I agree with Bear, I just see the output connected to two current sources between the rails. Or are the current sources a function of the strange looking rectangular bar with a + next to the top of it. This is beyond what I'm familiar with, could you explain the current sources?
Humor me some more please - what real world implementation is a CCCS with a "- 1" (inverting?) that runs off the same rail as a "+1"? Am I to presume it reduces current with drive? 
Or? Perhaps it takes a negative going input and makes it positive or vice-versa?
Don't think I've run across these CCCS thingies so far - a new one on me!
And, ok, I'm behind the curve - I admit it - is this whole circuit all current gain until the 1k output resistor?
_-_-bear
(I ought to read the patent...
)
Or? Perhaps it takes a negative going input and makes it positive or vice-versa?
Don't think I've run across these CCCS thingies so far - a new one on me!
And, ok, I'm behind the curve - I admit it - is this whole circuit all current gain until the 1k output resistor?
_-_-bear
(I ought to read the patent...
)
Bear:
If you lived in the world of spice sims these would be familiar (the symbols are always different-so much for standardization).
The current controlled current source is used here so that the impact of the rest of the circuit drops out. A cccs is a "perfect" amplifier, being just numbers. The real world implementation is (as they say) left to the reader.
Sims like this are great for testing ideas, I use a voltage controlled voltage source to test eq and feedback since its independent of the amplifier circuit. However its only a simulation. The real world transistors bring a host of problems that don't show on the simulation, even if the models are good. We were discussing transistor match on IC's earlier, something that highlights differences between real discrete design and tricks that work well on IC's. Plus extra transistors are essentially free and "frictionless" on an IC and bring cost, labor, matching real estate and additional failure rates in the real world.
If you lived in the world of spice sims these would be familiar (the symbols are always different-so much for standardization).
The current controlled current source is used here so that the impact of the rest of the circuit drops out. A cccs is a "perfect" amplifier, being just numbers. The real world implementation is (as they say) left to the reader.
Sims like this are great for testing ideas, I use a voltage controlled voltage source to test eq and feedback since its independent of the amplifier circuit. However its only a simulation. The real world transistors bring a host of problems that don't show on the simulation, even if the models are good. We were discussing transistor match on IC's earlier, something that highlights differences between real discrete design and tricks that work well on IC's. Plus extra transistors are essentially free and "frictionless" on an IC and bring cost, labor, matching real estate and additional failure rates in the real world.
I tried to live in the world of simulation, but as with virtual reality, it was difficult... still could not get into the VIP room no matter what... (oh wait, that was last night's dream...)
I use LTSpice, but I guess that is somehow a "junior" version, and not the real thing? A little OT, but are there non-
versions with these sorts of things installed? Or do I have to go and find the "model" and grab it to put it in... oh so many questions!
_-_-bear
I use LTSpice, but I guess that is somehow a "junior" version, and not the real thing? A little OT, but are there non-
versions with these sorts of things installed? Or do I have to go and find the "model" and grab it to put it in... oh so many questions!_-_-bear
bear said:......I use LTSpice, but I guess that is somehow a "junior" version, and not the real thing? A little OT, but are there non-
No need for $$$
Your LT Spice can do that as well.
Just look out for a component (as NPN, NJF, ...etc. ) called "f"
It's just that we have to figure out which CCCS refers to which <Vnam> in Edmonds circuit.
Tino
Is this thread becoming a Spice tutorial?
BTW, one can get a student version of MicroCap for free as well.
see: http://www.spectrum-soft.com/demoform.shtm
BTW, one can get a student version of MicroCap for free as well.
see: http://www.spectrum-soft.com/demoform.shtm
John, whenever you need a patent (and have the number), go to www.pat2pdf.org (note: org, not com) , you plug in the pat number and presto! you have it. A gem.
Jan Didden
Jan Didden
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