If you frequent our E2E forums they can be like detective mysteries. They are brain teasers that exercise and build your troubleshooting skills, solving analog problems with limited information. But not all these mysteries can be solved, given the information provided in the original posting.
“My amplifier circuit doesn’t work. Can you tell me what is wrong?” Seriously, that is nearly the extent of the information provided in some of our E2E forum postings. No schematic. No description of the problem.
If you are reading this blog, it’s a sure bet that you wouldn’t post a question like that example. Still, there is an opportunity to tweak the quality of information you submit on our forums to speed you to an accurate and complete solution. Here’s a checklist for possible items in your posting. Of course, most can omit some or many of these but consider the possible value that each may have in your inquiry:
Schematic— Word descriptions of circuits can be tricky, even if your circuit is very simple. There’s always a possibility of misinterpretation or confusion so it’s best to include a schematic. And the details you provide in your schematic can be crucial. Check out this example:
Power supply voltages— Your schematic may not show the power supply voltages and this can be important in solving many problems.
Oscilloscope captures— A picture is worth a thousand words. Be sure to provide scale factors and settings that could be important if they are not captured on screen.
Oscillations— If you are reporting a problem with an oscillation, its frequency and magnitude are valuable information in diagnosing the cause.
Noise— Merely reporting that you see excessive or unexpected noise is too vague. What is the magnitude? Describe it. Is it random thermal noise? Or is it correlated in some manner suggesting an oscillation or some external source? Again, a scope shot is best.
Product model numbers— Be sure to provide accurate product model number of all ICs in the circuit. You might need to use an IC from a competitor (rarely, I’m sure). We need to know.
Expected performance— Occasionally the reported results seem to fit the behavior of the circuit provided. Tell us what you expected the circuit to do.
Measured DC voltages— If your circuit seems totally out of whack, provide measured DC voltages to help us debug.
The load— Load conditions such as low impedance, high capacitance or long cables frequently influence circuits. Provide these details if it is outside the ordinary.
Bypass capacitors— If your schematic does not show bypass capacitors on the power supply, tell us that you have included them in your circuit.
Your troubleshooting efforts— Tell us whether you tested more than one IC? What else have you tried.
The TI engineers and other forum contributors who troll the forums are great at what they do. They’re knowledgeable and amazing at solving problems without ever physically touching your circuits. But they all flunked their Clairvoyant Troubleshooting class. Help them out with some quality information and they will speed you to a solution. And maybe you would like test and build your troubleshooting skills? Join us on the precision amplifiers forum. You may be the hero who helps solve a case. More tips on posting.
Did I forget something important on this list? Think about it and add it in a comment below. And, by the way, what’s the fatal flaw in the example circuit? (No TI peeps allowed.)
Thanks for reading,
Bruce email: thesignal@list.ti.com
Index to all The Signal blogs.
