T
Tim Shoppa
I've been using LM6181's to drive 50 ohm instrumentation interconnects
- typically a few feet of coax but sometimes longer - in the very low
tens of MHz with up to 5V or so swings. Works pretty well at the gains
I need (+2 to +10), is very stable into capacitive loads, and almost
all I know about high-speed medium-current opamps is based around this
chip and the cookbook recipes in National's app notes.
If I wanted to beef these outputs up - maybe up to 20V swing, maybe
better phase response to non-sine waveforms in the 20-30MHz region -
what's the next step up? When I asked this 15 years ago there were
higher-voltage specialty hybrids that did the beefier jobs, but I
honestly don't know if these exist anymore. There are lots of new
video amps that drive a volt or two into coax or twisted-pair into the
100MHz region but I don't see a lot of stuff beyond a few volts. I am
not incredibly price-sensitive (meaning I'm paying $2.00 each for the
6181's but if I found something twice as good at ten times the price
nobody would even blink, they'd just pat me on the back for doubling
the bandwidth and/or output swing).
Clearly I'm asking for twice as much swing, and twice as much
bandwidth, so I think I'm asking about 4 times the slew rate, right?
It's not that I'm unwilling to learn stuff beyond cookbook current-
mode op-amp recipes, but I'd really appreciate it if the cookbook
recipes I've been using in the past are directly applicable.
Tim.
- typically a few feet of coax but sometimes longer - in the very low
tens of MHz with up to 5V or so swings. Works pretty well at the gains
I need (+2 to +10), is very stable into capacitive loads, and almost
all I know about high-speed medium-current opamps is based around this
chip and the cookbook recipes in National's app notes.
If I wanted to beef these outputs up - maybe up to 20V swing, maybe
better phase response to non-sine waveforms in the 20-30MHz region -
what's the next step up? When I asked this 15 years ago there were
higher-voltage specialty hybrids that did the beefier jobs, but I
honestly don't know if these exist anymore. There are lots of new
video amps that drive a volt or two into coax or twisted-pair into the
100MHz region but I don't see a lot of stuff beyond a few volts. I am
not incredibly price-sensitive (meaning I'm paying $2.00 each for the
6181's but if I found something twice as good at ten times the price
nobody would even blink, they'd just pat me on the back for doubling
the bandwidth and/or output swing).
Clearly I'm asking for twice as much swing, and twice as much
bandwidth, so I think I'm asking about 4 times the slew rate, right?
It's not that I'm unwilling to learn stuff beyond cookbook current-
mode op-amp recipes, but I'd really appreciate it if the cookbook
recipes I've been using in the past are directly applicable.
Tim.
