Hello,

I have built a curve tracer from the Elektor magazine, the January 1996 edition to be specific.

I have two questions:

Are my PCB layouts acceptable? I am inclined to go with the SMD version as it is smaller. I know Poly capacitors have better tolerances and better temperature stability. Have I decoupled the power amp OK? I got the capacitance values from the datasheet. I fear oscillation because I initially wanted to use LM1875 but it just kept oscillating. TDA2030 was used instead. Should I go with a ground pour for the board?

When I leave the leads open, so no component being tested, The curve on the screen is 45 degrees. Can I presume that having built this on a breadboard what I am seeing is the result of the breadboard's capacitive properties? I know building it like this is not a great ideea but I was worried that I might run into issues with the AGC circuit, having substituted the BF245A.

Thank you!

 

I see no obvious faults in the PCB layouts. BUT I offer a concern about any SMT construction option, which is that surface mount assembly is much more demanding of solder skills, and that keeping track of the tiny parts is a lot more work.