Author Topic: current feedback op-amp recommendation ?  (Read 841 times)

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Offline jmelsonTopic starter

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current feedback op-amp recommendation ?
« on: July 16, 2020, 07:40:12 pm »
We have been using the AD8002 in some nuclear detector preamplifer circuits, and they work quite well.  Can anybody recommend one that has more output current?  The AD8002 is rated at 70 mA and does clip at about that level.  Is there a similar amp that can go to 100 - 120 mA output?  We need pretty fast risetimes in the 4-6 ns range, and may have to feed dual 50 Ohm loads with several Volt signals.  In this particular case, we don't need much amplification, but we need jumper-selectable inversion.

Thanks in advance for any suggestions.

Jon
 

Offline ni.st

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Re: current feedback op-amp recommendation ?
« Reply #1 on: July 17, 2020, 10:50:22 am »
What about the AD8009? I have used it to feed dual 50 Ohm loads, because it can deliver up to 175 mA. A downside would be, that it is not available in a dual package.
 

Offline OM222O

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Re: current feedback op-amp recommendation ?
« Reply #2 on: July 17, 2020, 01:26:33 pm »
The usual solution to that is to follow the op amp with a class A or AB amplifier (depending on power dissipation, crossover distortion, etc). Op amps aren't really meant to drive "high" currents (more than ~20mA) and your selection becomes very limited if you want to choose a high current op amp.
 

Offline jmelsonTopic starter

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Re: current feedback op-amp recommendation ?
« Reply #3 on: July 17, 2020, 01:50:17 pm »
NI.ST, thanks, I will look at the 8009.  Single channel part may offer advantages!

OM2220, thanks, I have used the Harris HA9P5002 buffer after a current feedback op amp with good results, but we need 4 ns rise and fall times here, and I don't think it can do that.

Jon
 

Offline E-Design

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Re: current feedback op-amp recommendation ?
« Reply #4 on: July 17, 2020, 02:15:59 pm »
We have been using the AD8002 in some nuclear detector preamplifer circuits, and they work quite well.  Can anybody recommend one that has more output current?  The AD8002 is rated at 70 mA and does clip at about that level.  Is there a similar amp that can go to 100 - 120 mA output?  We need pretty fast risetimes in the 4-6 ns range, and may have to feed dual 50 Ohm loads with several Volt signals.  In this particular case, we don't need much amplification, but we need jumper-selectable inversion.

Thanks in advance for any suggestions.

Jon

Since you only need to roughly double your output current, is there a way you can parallel share (ballast) two AD8002, preserving your speed characteristics while doubling the drive capability.
?
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Offline Mechatrommer

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Re: current feedback op-amp recommendation ?
« Reply #5 on: July 17, 2020, 02:43:41 pm »
We need pretty fast risetimes in the 4-6 ns range
what voltage swing range are we talking about? different swing, different slewrate requirement. opamp gives slewrate spec, not rise time. is 600MHz -3dB BW important? what nature of signal, repetitive? at what max repetitive frequency?
digikey search ymmv.
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Offline awallin

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Re: current feedback op-amp recommendation ?
« Reply #6 on: July 17, 2020, 05:11:04 pm »
LMH6702 works well for e.g. 10MHz distribution
https://www.ti.com/lit/ds/symlink/lmh6702.pdf
maybe two of them in parallel if you need more current?
 


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