Sampler diodes with more barrier height?

If elevated temperature is an issue, why not mount the sampling diodes on a peltier device?

The top gate would have the to-be-sampled signal which in my case consists of blazingly fast pulses flying by. A 10pF cap would really snuff them out. It's not a slow signal, doesn't have much content below a GHz.

It was one thought but that greatly increases power consumption, size and complexity. I'd rather use a higher barrier diode which would fix the problem. The Skyworks rep comes out here with some next week.

C47?

Second prize, two weeks?

Am 18.02.2014 17:41, schrieb John Larkin:

Hi, all,

are the still any SRDs that one can buy? Maybe certain PIN diodes that can be abused?

regards, Gerhard

Several people still make SRDs. M-pulse, Metelics, MAcom (all SRD makers start with "M")

MA44767 and MA44769 are SOT23 distributor items, 50-75 cents range.

Am 27.02.2014 16:02, schrieb John Larkin:

Ah, found them under varactors @Mouser, at least the MA144769-287T But 600 ps transition time is not that wonderful anymore, got half a ns from Fairchild NC7sz04p5x :-) Nobody escapes the CMOS steamroller!

thanks, Gerhard

The 44769 is rated 150 ps transition time, but they will go a bit faster if you drive them hard.

The fastest catalog items are around 25-30 ps.

Somebody makes some really fast 0402 sized parts, can't remember who.

Fast SRDs don't store much charge, so they are hard to drive.

Mouser currently has the MACOM MA144769, although they list it as a varactor diode. It's a buck per, in full-reel quantities... two bucks or so in small quantity.

Have you tried that? My experiments along those lines have been disappointing.

PHEMTS switch screamingly fast, and the gates are relatively easy to drive. Good SRD drivers. In the old tek samplers, they usually used an avalanche transistor to drive the SRD. HP tended to use a transistor driving a slow srd driving a fast srd.

Not with the BFP yet but with a BFR92 and it performed quite nicely. What happened in your case? How did you drive them?

I want to keep things simple. PHEMTs are nice but need a lot of fast gate swing unless followed by an SRD. BJTs almost snap from zero to saturation withing about 100mV on the drive ramp. I don't really care about saturation and recovery because the PRF is low.

BJTs are often used for cheap transmitters at UHF or above. Example:

Compression is at +20dBm at 2GHz which is pretty much full swing. Some of the MMIC should also be able to do this but unfortunately have a different pinout. Northrop-Grumman makes massive (and probably very expensive) BJT if you need tons of pulse energy for pulsed radar: