Hi:
I have a bunch of Intersil CA3096AE left in my drawer in DIP packages. I need the same thing in SOIC. I'd like to build an adaptive trigger such as the one Linear Technology likes to put in many of their comparator datasheets:
LT1394:
Does one need matched transistors for this, or is their choice of the CA3096 just a convenience of packaging, and I could get away with two each of 2n3094/2n3096 ?
Thanks for input.
-- Good day! ________________________________________ Christopher R. Carlen Principal Laser&Electronics Technologist Sandia National Laboratories CA USA crcarleRemoveThis@BOGUSsandia.gov NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
Forgot to mention that this part is discontinued.
-- Good day!
________________________________________ Christopher R. Carlen Principal Laser&Electronics Technologist Sandia National Laboratories CA USA snipped-for-privacy@BOGUSsandia.gov NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
I suspect you could use diodes for Q1 and Q3, and any old NPN and PNP for Q2 and Q4 -- but Zetex makes matched pairs, which Digi-Key sells.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html
This circuit (figure 18), which is said to operate to 45MHz, looks like it could well benefit from fast low-capacitance transistors for the bipolar peak-follower function. Sadly Intersil no longer offers the ca3096, but they do offer the hfa3096, which is a high- speed RF-transistor array replacement, featuring three matched 8GHz NPNs and two matched 5.5GHz PNPs, in a 16-pin soic package, available from DigiKey, at $3.18 each. While I do agree with Tim that these transistors don't have to be well matched, it certainly can't hurt, and will likely extend low-signal-voltage operation.
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Thanks,
- Win
Yeah, I saw those UUHF arrays.
So the point is, there is nothing *bad* about using the excessively fast transistors?
I guess I was worried about the possibility that such transistors can become oscillators in frequency ranges where I wouldn't even be able to measure with my lowly 500MHz scope, yet the occurence could manifest as peculiar and undesired behavior/malfunction.
Can one simply add a few pF of collector to base capacitance to make the transistors effectively slower if such silliness is suspected?
I don't know if I really need that adaptive trigger.
I actually used a much slower version of it once before in a free space optical transmission from an engine piston, where the brightness of the data was varying with the piston location. It worked quite well.
I have a simpler application now, just position sensing of a wheel where the sensors are in fixed positions. I can tune the gain and align the optics to make it work just right. But something about things that have to be tuned just right makes me feel unsatisfied.
Thanks for the input.
Good day!
-- _____________________ Christopher R. Carlen crobc@bogus-remove-me.sbcglobal.net SuSE 9.1 Linux 2.6.5
Well, they're fragile, and subject to ESD damage during handling.
BTW, they give the spec for a maximum high current, the transistors are slower at ordinary currents, for example 5.5 and 2GHz at 1mA.
Some added base-emitter capacitance, say 1.0pF, might be safer. Or you could run them at 100uA (Jim had to bias the old ca3096 at 2mA to get 45MHz). A well-placed feritte bead usually works.
I stock and use the attractive Panasonic smd PNP and NPN pairs, xn4401 and xn4501. These come in 6-lead 0.95mm sc-74 packages. They contain separate 2sb709 or 2sd601 transistors (50V, 50mA, 80MHz and 150MHz, 3pF), which are not explicitly matched, although they probably come from the same wafer. Maybe these parts would be a better choice for your application.
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Thanks,
- Win
[...]
Definitely would not do this, Win. Most parastic oscillators are running as a Colpitts using stray capacity and interelectrode capacity as the divider, and lead length in the base as the inductor.
The best bet is to minimize the length of wires connected to the device, especially the base. Then always add a 10 to 47 ohm series resistor at the base. This will kill bandwidth and risetime, but it's better than a parasitic that may come and go with changes in supply voltage, temperature, stray hand capacitive effects, etc.
JL recently mentioned having to add these resistors to a fabricated pcb. This can be a pain, so put them in the initial design.
Regards,
Mike Monett
Wasn't it the 3046 I used in that example?
The 3046 is on an absolutely ancient process with emitter sizes of 20u X 30u.
...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 | |
Sorry, Jim, I as referring to Jim (Williams, that is). His circuit required two each NPN and PNP transistors which he specified as in a ca3096 array.
Yes. What about the ca3096, same story?
--
Thanks,
- Win
Ok, thanks for the Panasonic part #s.
-- _____________________ Christopher R. Carlen crobc@bogus-remove-me.sbcglobal.net SuSE 9.1 Linux 2.6.5
I thought you were referring to my video amplifier example.
Likely.
...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 |
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