#garfield Logs

Nov 10 2023

04:18 AM VanUnamed_ is now known as VanUnamed
04:04 PM aandrew: hm...
04:06 PM aandrew: rue_mohr: do you have a favourite low pin count, low current voltage multiplier? I have a 0-4V analog signal I want to be 0-40V (actually 0-50 would be better). tiny current, but want the output to track the input
04:07 PM aandrew: my initial solution was the easy way: 50V boost regulator powering an op-amp set up as x12 or so
04:07 PM aandrew: input signal is practically DC; just the ouptut of a DAC I'm wiggling very slowly
04:11 PM aandrew: LED driver might be useful maybe
07:00 PM rue_mohr: oo
07:00 PM rue_mohr: hmm
07:01 PM rue_mohr: Its always been static voltages, let me think
07:30 PM aandrew: I actually learned about opamp bootstrapping
07:30 PM aandrew: all the examples are bipolar supplies but I might be able to get away with just one transistor and a pair of resistors
07:30 PM aandrew: have to play with it
07:31 PM aandrew: actually no that won't work because the opamp can't "ride" the output with only one transistor
07:31 PM aandrew: have to do both positive and negative supply rails but I can allow the negative rail to just go to zero
07:32 PM aandrew: and then I thought I'm overthinking this, so why not just use a single npn transistor capable of vce=80V and use it as a cheap class A, I don't actually ahve to sink current at all
07:33 PM aandrew: basically there's a 3.3V ADC which is measuring a 48V battery supply; it's just dividing the 48V down again but I don't want to modify that circuit so I need to be able to provide a 0-48V voltage for it to measure
07:34 PM aandrew: I mean hell I could just use a mosfet and PWM it to create the voltage I want to measure
07:34 PM aandrew: yeah that's easiest
07:34 PM aandrew: I'll just do that, no DAC or op amp needed, just a 50ish V supply
07:36 PM aandrew: actually... if I'm PWMing it I can just make my own shitty boost regulator with a mosfet and inductor and resistor divider feedback
07:36 PM aandrew: man all I had to do was rubber duck this I guess :-)
07:49 PM aandrew: also these breadboards I got from microcenter are kind of shitty
07:49 PM aandrew: the contacts are fairly wide which means thinner wires don't "grab" at all
09:31 PM aandrew: https://ibb.co/RB8fzf6 and https://ibb.co/0KPHq1v; it seems like it should work but the vds on that mosfet is way too high
09:33 PM aandrew: I tried to do a voltage doubler or even tripler on the output but I couldn't get it to work