/diy/ - Do It Yourself

>>1232132
Alright, just a couple of questions more. Firstly, will an LM-317T be good enough to act as the voltage regulator that creates the 2.5V ground for the opamps? I'm pretty sure it will be going by the specs, so I guess this question is more "has anyone done it and how well did it work?". I've never actually used LM-317s, oddly enough, but I understand the basic principles of operation, and it looks like I should be using larger values of the two resistors for more output accuracy, not to mention lower quiescent current. I can't just use a voltage divider because the caps required to keep the ground stable with respect to the voltage rails when running a <1Hz oscillator were ridiculous. Needless to say, nobody sells any 2.5V fixed regulators near me.

My second question, since 2N7000s are by far the cheapest (MOS?)FETs I can buy where I am, are they a good fit for the main switching transistor here? For this task the current will be less than 200mA for sure, switching voltage of possibly below 3V, not high frequency, just as you see. I have the option to save 5c a piece if I buy TO-92s instead of TO-220s, but I think I'll buy a bunch of both LM-317Ts and MOSFETs, and having the higher heat capacity will surely help in future projects, and it's also 5c off each if I buy 10 of them. Still, $9.50 NZD for 10 2N7000s isn't that great by the sounds of it, same with $14.30 for 10 LM317s. This is assuming it's handy to have 9 2N7000s lying about.

Also I think I will keep the buffer U2 in place, as it will let me run a small speaker off it as an electric horn, which leads me to my bonus question, are good horn frequencies (500Hz to 5kHz, I guess?) good for LED PWM? I'll probably run a common emitter amplifier off the buffer to get the extra volume.