op-amp suggestions - 20MHz, 30mA, hi-z output

Ken Smith wrote...
The requirement wasn't clear but I wonder if the LT1206 wouldn't do
the job. It isn't exactly low cost, but it may run cheaper than a
multicomponent circuit. I believe that the LT1206's output is high
impedance when you disable it.
Click to expand...
Yes. "In the shutdown mode, the output looks like a 40pF capacitor
and the supply current is typically 100uA." A nice part, I added it
to my table. I like the LT1206CT7's TO-220 package, with its 5 C/W
thermal resistance. One possible issue, it's a current-mode opamp.

part f_T Vsupply Iout slew tristate
number manuf MHz max max V/us output? comments
------ ----- --- ----- ---- ---- ------- ------------
LT1206 LTC 120 36V 500mA 900 yes current mode
CLC431 NSC 120 33V 60mA 2000 yes G = 2 min
CLC411 NSC 200 36V 70mA 2300 yes +/-6V Vout max

And one huge advantage for the LT1206 over the CLC parts, it's not
discontinued! In stock at DigiKey for $5.42 qty 25, $4.35 qty 1k.
That's a pretty reasonable price.


--
Thanks,
- Win
 
In article <csr6iv0q7e@drn.newsguy.com>,
Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
[....]
Yes. "In the shutdown mode, the output looks like a 40pF capacitor
and the supply current is typically 100uA." A nice part, I added it
to my table. I like the LT1206CT7's TO-220 package, with its 5 C/W
thermal resistance. One possible issue, it's a current-mode opamp.
Click to expand...

Go back a level for the table.

The LT1206 also drives reactive loads, capacitive and inductive, without
going silly. A lot of parts that drive capacitive loads ok have trouble
with inductive loads.


--
--
kensmith@rahul.net forging knowledge
 
Ken Smith wrote...
Winfield Hill wrote:
[....]
Yes. "In the shutdown mode, the output looks like a 40pF capacitor
and the supply current is typically 100uA." A nice part, I added it
to my table. I like the LT1206CT7's TO-220 package, with its 5 C/W
thermal resistance. One possible issue, it's a current-mode opamp.

The LT1206 also drives reactive loads, capacitive and inductive,
without going silly. A lot of parts that drive capacitive loads
ok have trouble with inductive loads.
Click to expand...
And there's the LT1207, which is a dual LT1206 in a 16-pin soic.
BTW, both the LT1206 and LT1207 have thermal shutdown circuits.


--
Thanks,
- Win
 
Jim Thompson wrote:
On Wed, 19 Jan 2005 15:57:06 -0500, John Popelish <jpopelish@rica.net
wrote:

More like a fet based relay.

Hey! Hey! Hey! Hey! A technical discussion. Will miracles never
cease!

As I said before, I'd use booster discretes at the output, making it a
piece-a-cake to tri-state.
Sounds good. The devil would be in the details of opening the
Click to expand...
feedback loop and the recovery on closing it, again. Especially if
this had to happen quickly or often.

--
John Popelish
 
On Wed, 19 Jan 2005 13:40:58 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On Wed, 19 Jan 2005 10:44:24 -0800, John Larkin
jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

On Wed, 19 Jan 2005 10:05:58 -0700, Jim Thompson
thegreatone@example.com> wrote:

On Wed, 19 Jan 2005 08:13:28 -0800, John Larkin
jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

On Wed, 19 Jan 2005 09:36:21 +0000, Malcolm Reeves
mreeves@fullcircuit.com> wrote:

Hi,

I need an op-amp to drive 30mA, on 24V supply, signal is quite high
frequency, 120kHz so I reckon I want at least 40dB to give low
distortion, i.e. at least GBW 20MHz but 200MHz would be better.

TI has lots of +-15 rail opamps that are *very* fast. THS3061 and
such. Fairly cheap.

also need to be able to turn the output high impedance.

*That* I don't understand.

John

He needs to "tri-state" his OpAmp.

...Jim Thompson


Think that's what he meant? Downstream analog switch, then.

John

Malcolm said "30mA". That's a bit rough with an analog switch.

...Jim Thompson
Click to expand...

Not any more. Some of the parts are down to 1 ohm. And I suppose you
could also use an SSR.

John
 
On Wed, 19 Jan 2005 14:58:44 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On Wed, 19 Jan 2005 16:42:05 -0500, John Popelish <jpopelish@rica.net
wrote:

Jim Thompson wrote:

On Wed, 19 Jan 2005 15:57:06 -0500, John Popelish <jpopelish@rica.net
wrote:

More like a fet based relay.

Hey! Hey! Hey! Hey! A technical discussion. Will miracles never
cease!

As I said before, I'd use booster discretes at the output, making it a
piece-a-cake to tri-state.
Sounds good. The devil would be in the details of opening the
feedback loop and the recovery on closing it, again. Especially if
this had to happen quickly or often.

Yep! Malcolm needs to provide more details.

...Jim Thompson
Click to expand...

It's surprising how many people post a question and then vanish from
the thread.

John
 
Jim Thompson wrote:
On Wed, 19 Jan 2005 10:44:24 -0800, John Larkin
jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

On Wed, 19 Jan 2005 10:05:58 -0700, Jim Thompson
thegreatone@example.com> wrote:

On Wed, 19 Jan 2005 08:13:28 -0800, John Larkin
jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

On Wed, 19 Jan 2005 09:36:21 +0000, Malcolm Reeves
mreeves@fullcircuit.com> wrote:

Hi,

I need an op-amp to drive 30mA, on 24V supply, signal is quite high
frequency, 120kHz so I reckon I want at least 40dB to give low
distortion, i.e. at least GBW 20MHz but 200MHz would be better.

TI has lots of +-15 rail opamps that are *very* fast. THS3061 and
such. Fairly cheap.

also need to be able to turn the output high impedance.

*That* I don't understand.

John

He needs to "tri-state" his OpAmp.

Think that's what he meant? Downstream analog switch, then.

Malcolm said "30mA". That's a bit rough with an analog switch.
Click to expand...
More like a fet based relay.

--
John Popelish
 
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