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SMT DIP adapter PCB from TI

PA3COR TI SMT DIP adapter EVM

If you like prototyping but find it’s a nuisance to mess around with small, all too common, SMT packages, the Texas Instruments SMT DIP adapter kit might be something for you.

The DIP adapter kit supports six of the most popular industry-standard packages, including:

  • D and U (SOIC-8)
  • PW (TSSOP-8)
  • DGK (MSOP-8, VSSOP-8)
  • DBV (SOT23-6, SOT23-5 and SOT23-3)
  • DCK (SC70-6 and SC70-5)
  • DRL (SOT563-6)

There are six coupon boards per supported package type,  so in total 30 adapter PCBs. It comes complete with terminal strips. Best of all it costs only $10.00 USD!

You can find more information or order the SMT DIP adapter kit HERE

PS
I don’t have any stock or interest in TI, nor do I get paid, I just found it a neat and cheap solution.

Do-it-yourself SMT prototyping board

PA3COR SMT Prototyping board

Frequently, I need to do some SMT prototyping. Partly because some components are only available in an SMT enclosure (like the MCP4725, a nice small 12 bits DAC), partly because it needs to be small and sometimes it is Saturday 5 past 5 and the only type of a critical part available is SMT. Two weeks ago I saw on SMD shop a SMT prototyping board.

It features pads in 0.05″x0.05″ square pattern and every fourth pad is connected to the groundplane on the bottomside.
Looks quit nice, with the only drawback a price tag of 8.22€ for 100 X 80 mm board. (yes I am a skeap skate dutchie). Nowadays, you can order 10 pieces of 50 mm x 50 mm PCB for around €10 in China. So, I figured, why not design your own?

Below you see the result. the first figure is the top layer

PA3COR SMT Prototyping board - top view

The pads are laid out in a 0.05″ pattern an do have a size of 0.042″ by 0.042″. Every fourth pad there is a hole to the bottom layer. The holes are non-plated-through. If you want to connect them to ground just stick a small wire in and solder it at both ends.

And here is the bottom layer, which is usually used for ground layer.

PA3COR SMT Prototyping board - bottom view

Have fun! If you would like to receive the gerber files, let me now!

Update : you can download the Gerber files for the SMT prototyping board HERE !

HP-456A Current probe – repair

This HP-456A current probe is a real beauty. Released as a new product by the Hewlett-Packard Company in 1960, the 456A was HP’s first solid-state, stand-alone, clip-on current probe. Its elegantly designed amplifier uses two— then “state-of-the art”—PNP germanium transistors. The Original Probe In 1960, The Hewlett-Packard Journal (July-August, Vol. 11) proudly announced: “This new probe measures current over the full range of the frequencies most commonly used in typical work—25~ to 20 megacycles—and over an amplitude range from below 0.5 mA to 1 A rms.

HP-456A product

Below you’ll find the circuit diagram of the HP-456A probe.

HP-456A circuit diagram

Maybe the concept of the circuit is unclear at first but actually the idea behind it is really simple and effective. (Especially considering the fact that this performance was achieved, with what would be considered nowadays, mediocre components at best.)
Q1 functions as the input transistor in common base configuration. As you will know in a CB setup, the base is hold at a fixed voltage (0V in this case), the emitter is used as the input and the collector is used as the output. Main characteristics (and in this advantages) are the low input resistance and the high frequency. The latter is caused by the fact that the base is at a fixed voltage effect and the Miller effect is eliminated. Also because the emitter current equals the collector current, there is no current amplification.
Q2 is the output amplifier and is set up in a common emitter configuration (emitter hold at a fixed voltage).
The combination of the two transistors works as op-amp in current to voltage topology (eq. transimpedance configuration.) See below of sketch of the amplifier configuration used in the HP-456A :

transimpedance a,plifier

Rf is implemented as R9 parallel tot R10. Beautiful isn’t it?

The reason the setup didn’t work in the one I bought is that the cable actual current probe was broken on were it connected to the PCB in the amplifier case. (in the circuit near C2 and C3). After fixing this it works like a charm. Not bad for a 25+ years old device!

I you have any questions let me know!