The TL08x is a work-horse FET input amp but I'm looking for a jellybean CMOS/FET input amp that's a bit better on the GBW and slew rate for not much more money.
Yer standard TL082 has 4 MHz GBW and 13 V/usec slew rate. A couple candidates for around a dollar each in quantity are the TLC082
and the TSX920
the former TI part is a bit more expensive...which would be your choice or any other suggestions?
the application at the moment is I was just curious and looking at the waveforms from some small signal thyratron tubes in relaxation oscillator configuration - lil tubes like the 2D21 actually have ripping fast edges when cutting out, I wasn't expecting them to be that savage. a bog standard FET input op amp buffer can barely keep up.
But would be good kind of part to have on hand in general
Both of those are 16V parts, compared to TL082's 36V. If that's OK, I like the TSX920, speedy and inexpensive.
Not so much enthusiasm for the TLC082. Here's what I said about TLC082 vs TL082, on a thread here in 2006.
Usually when a manufacturer makes an IC family using a part number that's a takeoff on another popular part, such as the TLC082 compared to the TL082, they retain as many of the main features as possible. For example, these two opamp families have similar slew rate. But here TI does an unusual thing; whereas the TL08x JFET opamp's input common-mode range is to +Vcc, the TLC08x CMOS input range is to -Vee.
This is the kind of thing could really catch someone who was making a substitution. Perhaps LMC324 or TLC324 might have been a better name for the TLC084, and TLC358 for the TLC082.
Other things that might catch one up would be the 36V maximum supply-range reduced to 16V, and the rather high 23pF input capacitance of these CMOS parts. 23pF is high enough to make a low-gain amplifier using commonplace 10k feedback resistors ring like a banshee, from the unexpected extra 700kHz pole at the input. The TL08x opamp doesn't suffer from this pole, but even if it did one might not notice, due to its slower (3MHz compared to 10MHz) speed.
The high input capacitance is one of the penalties for lower noise, 8.5nV for the TLC08x, compared to 18nV for the TL08x.
It's a curious design choice: most users must be attracted to this family for its speed, or its 50 to 100mA rail-rail output capability, rather than a reduced but still fairly-high noise. If TI's designers had used say 6x smaller input transistors, the capacitance would have been a relatively-innocuous 4pF and the noise would have been similar to its TL082 namesake, which people have accepted OK. And the die would have been smaller (the TLC082 costs $1 qty 100, 40% more than the JFET TL082).
We don't use duals much. PC layout is nice when you can put one SOT23 amp wherever it fits best. And there is always the agony over tying off an unused section.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
I find the packaging on duals to be painful too. I almost always use singles in SOT23s or quad TSSOP-14s. Space is always a premium (and I have boards with 40 or 50 opamps).
TI hasn't been consistent in specifying input capacitance, which they don't list on the TL082 datasheet at all. Some of the earlier ones list a differ ential Cin, some of the later ones list differential and common mode Cin, a nd this TLC082 lists only a common mode Cin. The common mode Cin has always been high, in the range 10-20pF, and the differential has always been cons istently low in the range of 4pF where it's even listed, which makes sense. It doesn't look like the reduced stability due to the common mode Cin of t he TLC08X is as bad as you make it out to be, the TL082 is probably just as high. And where is the CMOS in the TLC08X? Their SPICE model listing uses PJF, P- channel JFETS, for the input differential amplifier, and their schematic sh ows the same. Datasheet drops every buzzword known to man in automotive electronics. Lik e the TLC08X is really going to make Advanced Driver Assistance short range radar happen on its own. I don't see a one of them in their reference desi gns. Sheesh.
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