aaron_do wrote on May 30th, 2008, 1:58am:I need some kind of buffer with SMA inputs with an input capacitance of no more than 2 pF to work up to 10 MHz.
As far as you connect an amplifier to DUT via 50ohm coaxial cable, a capacitance loaded to DUT is far larger than 2pF even though an input capacitance of amplifier is 2pF.
Or you expect 50ohm impedance of amplifier ?
What signal do you want to observe ? Oscilloscope ? Spectrum Analyzer ?
aaron_do wrote on May 30th, 2008, 1:58am:Does such a buffer exist, or do i need to design on-chip buffers?
I use active high impedance probe both for Oscilloscope and Spectrum Analyzer.
There are many excellent probes available.
Or I use OP Amp of ADI. Then connect DUT to OP Amp with very short line on board.
I often use following.
http://www.analog.com/UploadedFiles/Data_Sheets/AD8138.pdfMaybe AD8138 is too over spec for your purpose. You can find reasonable one in ADI's products.
But maybe on-chip buffer is most cheap.