document updated 18 years ago, on Apr 5, 2006
Requirements
- Low power consumption if possible
- Current-limited output if possible
- Electronic control of voltage output
- Electronic control of frequency / pulse width
Output
To get actual pain, there are posts on the internet that suggest you need to go as high as 90v... that normal TENS units are ~40v. So you have to use a step-up transformer with an oscillator.
Apparently transformers get a little pissed when you give them straight square waves.
So, the output will have to be some combination of D/A conversion to produce a modified sine wave (a triangle wave might work?), a transformer, a fast PWM output, and a common emitter switch or amp to combine them.
Todo
- Figure out R-2R DACs and why they need a summing amplifier, etc...
- See slides on the DAC800 and how it's wired up
- Maybe even figure out the hows/whys/whats of op-amps.