Does anyone of you may be able to provide a simple discrete circuit for a sawtooth circuit....500k Hz frequency with a variable amplitude. I have done my research but have not found a reliable one. thank you
I was thinking that too. 500 KHz isn't out of the range of the 555, depending on the particular technology ( not going to look it up ) I have one running at 500 Khz on a nasty breadboard right now.
I happen to remember the specs from an NE555 PDF, max listed frequency is 500khz. Would depend on the exact 555 you had but I'm sure there's a bit of wiggle room there.
Anything that just charges a capacitor through a resistor (Unijunction, 555) will not produce a linear sawtooth beacause the voltage vs time is an exponential function.
It takes an integrator (opamp), or a current-source charging a capacitor to create a linear voltage vs time function.
There are many circuits out there that just a modicum of searching will uncover.
Anything that just charges a capacitor through a resistor (Unijunction, 555) will not produce a linear sawtooth beacause the voltage vs time is an exponential function.
It takes an integrator (opamp), or a current-source charging a capacitor to create a linear voltage vs time function.
There are many circuits out there that just a modicum of searching will uncover.
If you want linear from a UJT , 555, ete, you have to charge the cap with a current regulator. Here's one I'm using, J310, I didn't try for 500kHz yet, if I remember, I'll try today, but with a little adjustment you can get a pretty good saw tooth with a fairly sharp bottom tooth.
Kinarfi
Anything that just charges a capacitor through a resistor (Unijunction, 555) will not produce a linear sawtooth beacause the voltage vs time is an exponential function.
It takes an integrator (opamp), or a current-source charging a capacitor to create a linear voltage vs time function.
There are many circuits out there that just a modicum of searching will uncover.
If you want linear from a UJT , 555, ete, you have to charge the cap with a current regulator. Here's one I'm using, J310, I didn't try for 500kHz yet, if I remember, I'll try today, but with a little adjustment you can get a pretty good saw tooth with a fairly sharp bottom tooth.
Kinarfi
Well I tried to get to get 500KHz out of a PUTJ 2N6027 and only got up to 211KHz and that was with 3 10pf caps in series. Scope shot attached,
I also said that if you charge a cap with a constant current you would get a flat ramp instead of the rc time constant ramp, not so sure now, I know I have in the past but I couldn't do it today. I put a resistor in the circuit and measured the amps and took a picture of it, then replaced the resistor with a 3 terminal current regulator LM334 and adjusted it to the same current and took another picture, put the on the same picture, attached.
Kinarfi