AD8307 Version 3 Board

It took a while but I finally got a board that is close to a final version. Version 3.   

Version 2 board was etched and I started to populate but after about 4 components I realized that there were too many short comings and it was not work the effort to complete.  

Version 3 is a redesigned board and all components are now smd.  New is a lpf on the output of the 8307 to protect the adc from any rf.  I think the filter may need to be reworked somewhat but that will be later on and after running some simulations in LT Spice.  As well I installed the additional components in the front end to extend the range up to the 500mhz level.  While I’m not that interested in frequencies that high, I wanted to see if there was any improvement in the HF range.  From 1mHz to 30mHz there was a drop of 1dBm and although that’s not much in the scheme of things, why not try and see if I can make an improvement.

The board was a little challenging to build as I went with smaller traces. But, the tighter clearances were the main issue.  So as I installed each component I checked for shorts with an ohm meter. Probably not a bad idea anyway but adds to the time. The lpf resistors are 603’s and that was an interesting exercise for installation. They are a little cockeyed but since they weren’t shorted to ground I was happy and left well enough alone.

Results so far are ok. The bottom end is not as good as ver 1 and have a couple of things to check for that.  Front end component that I added, the lpf, or maybe even the 8307 chip.  The chip is a smt version from eBay and the ver 1 board had a dip package type I bought from Digi Key.

Due to the 15uf cap causing a large draw of power, I let the smoke out of the smt regulator. In the meantime I had wired up the TO-92 type until I figured out the problem. The traces are now a little worse for the wear unfortunately. As well the pinout is incorrect on the board but I can get around that by putting the regulator on its back. Correct that in version 4.