Re: Bypassing

On Sat, 10 Jan 2009 13:58:20 -0800, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

John Larkin wrote:
On Sat, 10 Jan 2009 12:58:29 -0800, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

John Larkin wrote:
On Sat, 10 Jan 2009 11:25:51 -0800, Bob Penoyer
<bob@xxxxxxxxxxxxxxxxxxxx> wrote:
[...]

This is a very unusual configuration. It suggests to me that the guy
who wrote the datasheet experimented and found that this configuration
worked for him when other configurations didn't--in his particular
set-up. Why else use the series resistor?

This suggests that the part has some stability problems that even the
applications engineer had a hard time dealing with.
This opamp has an 18 GHz *closed loop* gain-bandwidth product. It has
a right to be pickey.

And all that for under four bucks. TI came out with some great amps. Now
if they only had piped out the IN- directly ...


That node probably can't be brought to a pin.


I was hoping pin 12 could do that with pin 13 VS+, but probably you are
right, this can become iffy.


On our latest gadget, we aren't grounding the IN- pin, but bypassing
it hard and driving it from a trimpot + c-load opamp, to use it as a
DC offset trim. Wish us luck.


That's one of those situations where your new PADS guys can test his RF
skills :-)

Girl. The Brat, in fact. Her first board was a 4-layer, 1.5 GHz, G=100
amplifier. Wish us luck.

The best pcb layout people I've known were women.


The TI rep has told us that standard analog remains a very important
part of their biz. Looks like they got beat up on cell-phone parts
(huge volume, zero margin) so are going back to customers like us for
revenue. They do have the fastest 30-volt process on the planet.


Yes, and on one project I sure was glad they do.

Lest I repeat myself... do NOT use THS3062!

John

.

Relevant Pages

  • Re: Bypassing
    ... who wrote the datasheet experimented and found that this configuration ... applications engineer had a hard time dealing with. ... That node probably can't be brought to a pin. ... it hard and driving it from a trimpot + c-load opamp, ...
    (sci.electronics.design)
  • Re: Bypassing
    ... who wrote the datasheet experimented and found that this configuration ... TI came out with some great amps. ... I was hoping pin 12 could do that with pin 13 VS+, but probably you are right, this can become iffy. ... I also worked with several women who were excellent layouters. ...
    (sci.electronics.design)
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  • Re: Bypassing
    ... who wrote the datasheet experimented and found that this configuration ... I was hoping pin 12 could do that with pin 13 VS+, but probably you are right, this can become iffy. ... When we discuss an RF critical layout after giving him my schematic and netlist we usually talk about RF-tight areas for one minute and then another four about politics. ... millivolt offset, <<1% gain accuracy, low distortion... ...
    (sci.electronics.design)
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