Recent content by kvtb

  1. K

    Sine wave with variable frequency

    Hi, thanks for your replies. Very interesting discussion. When I plot sin(2*pi*(-10*exp(-2t)+4t)), I get exactly what I want/expected. But... elibj123, how did you get to this: -10*exp(-2t)+4t ? When I calculate [f(x)*x]' I get something else, namely...
  2. K

    Sine wave with variable frequency

    I'm trying to do something very simple... I'd like to have a sine function, where the frequency is controlled by a separate frequency function Something like this: g(t) = sin(2*pi*f(t)*t) Assume that f(t) = 20*exp(-2*t)+4 I would expect a sine wave that starts at 24 Hz and then...
  3. K

    Equation for BJT voltage controlled amplifier

    Hi, the trig signal is a +5V pulse, duration is 2 msBTW, in mean while, I've tried to 'measure' a transfer function (as function of Vb and Vc) and tried to fit an equation on top of it. I'll post results later.
  4. K

    Equation for BJT voltage controlled amplifier

    dlgoff, turin, thanks for your replies. let me try to explain the circuit in the link I've given, using another link; http://mitglied.multimania.de/raf909/rimshot.htm the three op-amps and surrounding capacitors and resistors are sine wave generators, these generate a sine wave (at three...
  5. K

    Equation for BJT voltage controlled amplifier

    turin, cabraham, thanks for your replies. I think my question was perhaps not clear or incomplete: turin: The schematic is just a small part of a larger schematic to illustrate my question, that's why there's no ground. If you interested, please take a look at transistor Q65 in cell J8 of...
  6. K

    Equation for BJT voltage controlled amplifier

    Hi, as mentioned in my previous thread, I'm currently busy with a 'small' project of translating an analog device (synthesizer, based on schematics) into a digital (software) version. I know 'nothing' about EE, I'm a Computer Science guy, so hopefully this question is not too easy :-) This...
  7. K

    Incomplete transfer function for phase response

    @uart and The Electrician. As a non-EE I'm quite impressed by your analysis of the schematics. I'll try to perform a manual z-tranform based on the transfer functions you've supplied. Thank you.
  8. K

    Incomplete transfer function for phase response

    hello uart, I'm currently using qucs (http://qucs.sourceforge.net), but I'm considering re-simulating the same circuit in GNUcap just to be sure the software is not an issue here. I indeed think that the circuit I'm simulating is the same I've posted here. Because just by looking at the...
  9. K

    Incomplete transfer function for phase response

    gentlemen, your hints brought me back on the right track. it could be a lucky shot, but found that a small change to the transfer function would give a perfect fit: H(s) = \frac{s^2 + a s}{s^2 + \omega_0/Q s + \omega_0^2} a new term has been added to the numerator: a s The...
  10. K

    Incomplete transfer function for phase response

    Dear berkeman, thanks for your reply, the original circuit can be found here: http://hardware.freepage.de/cgi-bin/feets/freepage_ext/339483x434877d/rewrite/raf909/rimshot.htm or here: http://www.kolumbus.fi/janne.husu/specs/909va.gif (in j9/j10)
  11. K

    Incomplete transfer function for phase response

    Hi, I'm currently busy with a 'small' project of translating an analog device (synthesizer, based on schematics) into a digital counterpart. What I do is basically simulate the device using a SPICE model. Then I look at the outputs, and see if can fit some equation on it. Based on the...
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