In article , john jardine wrote: [...]
The LH0063 IIRC ws even faster. I actually did get to use LH0033s. They were quite nice about improperly terminated lines.
-- -- kensmith@rahul.net forging knowledge
See figure 2.48
Yes.
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Thanks,
- Win
nice piece of hardware , but is not present in your book :-)
Mr Hill , many thanks for your work, it's an enourmuos collection of info on electronic technology ( I have some doubt about the WOM memory .... )
I think to reserve this design for another application where I probably need a bit more output voltage and current
but I need some clarification
1) can I use non SMD parts, good old 2n2222 etc. ?2) can I modifie the feedback network ( 499 - 499 resistor ) or even consider the circuit as a discrete component OA ?
3) can I parallel some more output transistor ?at +-25 volt supply can be a very nice beast
I am bit curious too , the power pad is around 2mm x 2.5 mmm
perhaps I will use a small strip of copper but .....
I the meanwhile I found two interesting chip from texas 'improved AD815'
ths6032 ths6012
so-powerpad too but a bit bigger ....
do the paralleling of op amps is a routine ( with output resistors ) or not ?
Hello Ken,
They are great. But I guess the market for those was too small.
Regards, Joerg
Which PNP are you referring to, the input PNP long-tail differential pair? It's base would be at +5V. Oops! That doesn't work at all!
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Thanks,
- Win
Well, they make the best current sources. I get 20 transistors, unless one wants to add two more for reliable performance, then it's 22 transistors total. Not so many in the IC world, nor in our new SMT machine-assembly "parts-are-free" world, either.
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Thanks,
- Win
You really need a pc board to test parts like this. Given that, a copper island under the chip, peppered with thermal vias to the ground plane (if a multilayer) and also to a 'thermal antenna' pad on the flip side. It doesn't take a lot of copper to cut the theta of an SO-8 by a factor of 3 or so.
Like most fast amps, these run out of swing at high currents and close to the rails, so you get droopy corners. If you back off on current enough to get crisp edges, the power dissipation per part is reduced, too. But then, the THS3062 gets pretty hot at Iq, so needs some heatsink help even of you don't load them hard. The 3-in-parallel situation is a pretty good compromise.
Somebody should make a universal pin driver: +-10 swing at least, LVDS input, programmable Vh:Vl, thermal limiting, fast/clean edges in the
5v/ns sort of range.John
not the Wilson current mirror .... but the high speed amplifier as a whole.
I was already aware of the presence in the book of the current mirrors as 'programmable' current source.
Something worries me about this circuit. I'm going to add voltages Modified:
It looks to me like the 9.3V on the collector of the PNP transistor would be forward biasing it. Did I miss something?
-- -- kensmith@rahul.net forging knowledge
Can you give us a typical R-theta for the setup you describe above?
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Thanks,
- Win
Nope.
John
This is the kind of circuit we refer to as "component rich."
John
Seems pretty SPARSE to me ;-)
The PORTION of a WiFi chip that I'm currently working on (just the limiting/log RSSI IF strip) has....
PMOS 6 NMOS 54 NPN 296 (SiGe) R 288 C 318
Counts in the 20's are simply farts in a strong breeze ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Sometimes an IC datasheet will include a component count. It's amazing to see (it's getting hard to type, with two new kittens walking on my keyboard. The Brat named them Ajax and Comet) numbers like "278 equivalent transistors" for an opamp or a simple logic part.
That's one reason that discrete circuit design (ie, not IC) is a dying art: most of the time, it makes more sense to buy ICs than to design with a bunch of discretes. So us circuit designers have to move up the abstraction stack, buy lots of cheap chips, and combine them into more complex stuff. I'm doing small PCBs that would have been racks full of stuff a few years ago. A few exceptions remain: high power, high speed, high voltage, RF.
Simple = elegant.
John
[snip]
I've been at IC design for so long, ~43 years now, that I have trouble doing cost-efficient discrete designs... I tend to use too many components... of course everything works textbook since, in my world, there are NO tweaks allowed.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
How about we remove the gain of 2:
Now the PNP still has a reverse bias on its collector but I'm still worried about it a bit. Many bipolars have a "dynamic saturation" effect where they slow down as the collector voltage gets down below about 2V. I don't off hand know to what degree XXX2907s have this effect.
How about: Vcc Vcc Vcc ! ! ! \\ \\ / / / \\ \\ \\ / / / \\ ! ! ! V ! ! --- ! ! ! !/ e !/ e +-------!----------!------ .... repeat as needed ! !\\ !\\ !/ ! in-! ! !\\ e ! ! ! ........ +--- +---------+------- Out ! ! ! . ! \\ \\ ! . / / / ! . \\ 50R \\ \\ ! . / / / ! . \\ ! ! ! . ! gnd Vee ! . Gnd ! .
----- Mirror line -----------
-- -- kensmith@rahul.net forging knowledge
What subtlety am I missing that keeps it from having big rail-to-rail current draw?
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Take a look at the board in a.b.s.e. It has two GigaLogic chips and two GaAs distributed amps, all power-padded and heatsunk. Ghastly.
John
Hello John,
Not always. It is amazing how much of the mundane stuff is still done in discrete. I was looking whether the time had come, after 10 years or so, to move one of the designs I had done for a client to a uC or maybe an ASIC. So I asked them what the current cost per board was. The answer blew me away. Maybe I'll look at the circuit again in another ten years.
Sometimes it is "cheap = better than elegant" ;-)
Regards, Joerg
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