When there is no USB, the opamp will be putting out a low, right? It will cause R3 to drop some voltage.
That is the –GS voltage which should turn on the opamp. Looks good to me. I would disconnect the output of the opamp and manually take the gate open and ground to see if it is turning on all the way properly. I always disliked high side switching circuits. From: [email protected] Sent: Friday, March 1, 2019 12:13 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] OT: EE Consultant Schematics attached. The main issue I'm having is when powered via USB, everything works fine. When powered via a 12V car battery, the chips seem to not have enough power. There are two comparator circuits, one to monitor USB/Batt and report how the unit is being powered. The 2nd actually provides the power. One chip will occasionally draw ~150-400ma of power causing the board to lock up. Chips are powered via Vin. What I don't understand is why everything works perfectly on USB but has issues when powered via 12V. On Tue, Feb 26, 2019 at 11:53 AM <[email protected]> wrote: Circle of stability, miller capacitance all good stuff. From: Mark Radabaugh Sent: Tuesday, February 26, 2019 9:48 AM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] OT: EE Consultant Oh sure, now you probably want me to believe transistors have states other than off and on. Mark On Feb 26, 2019, at 11:20 AM, Ken Hohhof <[email protected]> wrote: > And good luck finding an analog circuit guy anymore ;-) That’s what I was. Not much demand, that’s why I’ve been doing other things for over 20 years. Actually made the switch to engineering management in the 80’s but still did some design work for another 10 years because all the engineers wanted to do digital and processor designs. I still have the books, the brain is rusty though. I tried to convince the new engineers that high speed digital design meant knowing analog, RF and microstrip techniques, but they weren’t buying it. Getting their products through regulatory emissions testing did give them a bit of religion. I still remember laying out PCBs using red and blue tape. From: AF <[email protected]> On Behalf Of Mark Radabaugh Sent: Tuesday, February 26, 2019 9:09 AM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] OT: EE Consultant Yep - I’m qualified to answer some things and would be totally lost on others. EE has become a huge field with many many disciplines. And good luck finding an analog circuit guy anymore ;-) Mark On Feb 26, 2019, at 9:56 AM, Ken Hohhof <[email protected]> wrote: Analog? Digital? Even with those there tend to be specialties like emissions, safety, PLD/ASIC design, microprocessor/microcontroller, RF, etc. Or do you need a generalist? From: AF <[email protected]> On Behalf Of [email protected] Sent: Tuesday, February 26, 2019 8:33 AM To: AnimalFarm Microwave Users Group <[email protected]> Subject: [AFMUG] OT: EE Consultant Having an issue with a circuit design, anyone know a good electrical engineer they can recommend? -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com ------------------------------------------------------------------------------ -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com -------------------------------------------------------------------------------- -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
-- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
