What kind of device gives a suitable switch for a gated integrator operating in the 100MHz+ bandwidth region ? The to be integrated time window could be as short as 10ns. Common elements such as a mixer or just a diode have charge injection, offset problems, thermal dependencies and such.
The product is reliable and robust, but it is for a niche market. Signetics invented and introduced the lateral MOSFET a very long time ago, and I've used a lot of them over the years, mostly as the SD214.
Sadly, they didn't seem to sell in large enough numbers for Signetics to keep on making them. Philips did take over the technology when they took over Signetics but eventually stopped making the parts in one of their "rationalisastions". Linear System were one of several companies who stepped in to satisfy the small but persistent demand.
Impressive indeed, and the various internal capacitances are remarkably low, but not really low enough for 100MHz region.
I'd go for a diode bridge, or convert the signal to a current (plus off-set to keep it unipolar) and steer it through the tail of a long- tailed pair. The Harris (now Intersil) Gilbert cell IC (HFA3101) might be a place to start.
You can make amazingly strong mixers out of those.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
They have another type, the SST824, which has an impressive 5 Ohms Rdson and takes as much as 1 Amp and is to switch within 2ns. I'll be going to try it with a 50 Ohm MMIC as signal driver.
I once had to have a switch with ultra low injected charge and found that nice Fairchild's FSA66. Didn't tested it because I had a better solution to my pb so I don't know for the 50fC (yes!) figure but I read something elsewhere that let me think it is for real. Depending on your configuration it might be useful.
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