| Electronics > Beginners |
| transistor replacement for VCO? |
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| orolo:
The 2n2369 can be found in SOT-23 format for 0,056 euro each if you buy 100. I got from mouser a hundred recently. Really handy transistor for fast switching. |
| Yansi:
--- Quote from: FrankBuss on July 14, 2017, 06:46:54 pm ---I found the problem: I used 10 pF instead of 10 nF for the integrator capacitor. Looks good now, with 20 nF for lower maximum frequency: --- End quote --- No, it does indeed look bad. Guessing from the ugly distorted triangle sides, you have used a pisspoor ceramic cap for the integrator. that is a big NO! Never ever use pisspoor ceramic caps in any signal circuits. Use only foil type (any foil, is way better than ceramic). Ceramic are good only up to some nF when C0G / NP0 dielectric material is chosen. All other dielectric types are extremely voltage depndent and non-linear. |
| FrankBuss:
And finally the triangle-to-sinus wave-shaper circuit. The replacement parts work well, I just had to change a few resistors: Examples: Interesting: if I adjust the wave-shaper pot, I can smoothly change between sinus and square, or sinus and triangle: Full complete KiCAD circuit: http://www.frank-buss.de/tmp/vco.zip |
| FrankBuss:
--- Quote from: Yansi on July 15, 2017, 05:11:24 pm ---No, it does indeed look bad. Guessing from the ugly distorted triangle sides, you have used a pisspoor ceramic cap for the integrator. that is a big NO! Never ever use pisspoor ceramic caps in any signal circuits. Use only foil type (any foil, is way better than ceramic). Ceramic are good only up to some nF when C0G / NP0 dielectric material is chosen. All other dielectric types are extremely voltage depndent and non-linear. --- End quote --- Thanks, you are right, the curve could look cleaner. I will try to use foil capacitors. Don't have them in my parts bin, but I will order some for testing. Looks like Digikey has no foil capacitors as SMD (except one part)? Are there only through-hole foil capacitors? |
| RandallMcRee:
Digikey says 3,000+ film capacitors surface mount. Also, one of the really nice things about the Analog parts kit is that you cannot buy the individual components without having to, in many cases, also buy an adaptor and have enough skill to solder them. So, for me, a real bargain. Soldering SMT is not my strong suit. |
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