RE: DC Load "La Carga" Episode V Final Assembly and Testing

DAB — Wed, 12 Aug 2015 20:36:12 GMT

Looking good John.

I like the strong aluminum shell and the heat sink, you should be covered for heavy loads.

DAB

RE: DC Load "La Carga" Episode V Final Assembly and Testing

michaelkellett — Wed, 12 Aug 2015 08:10:55 GMT

Rather than use a huge value for C5 it would be better to keep it small and put a resistor in series with R16 and the C5/U1.2 node - because:

1) R16 is a very low value so your op amp (U1) is seeing a large capacitive load which will not improve its stability.

2) C5 is working into 0.5R so the amount of HF feedback you get depends on the open loop output impedance of U1 which is not constant with frequency or very well specced or controlled.

3) The additional resistor allows you to balance DC source resistances to U1 inputs (which probably doesn't matter with this design and op-amp but often does).

4) You can go back to using a nice small capacitor for C5 which in a commercial design would mean you could use a COG type surface mount cap costing less than 1p rather than a film type costing a great deal more.

5) Under fault conditions you could get big spikes across R16 which could damage the op amp but wont if there is a resistor in the way.

6) There is no downside to a resistor in that position [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-b4b259e2-6f29-4369-9801-86f10ebb4cf7/contentimage_5F00_1.png:16:16]