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http://ww1.microchip.com/downloads/en/Appnotes/00849a.pdf RS is a series resistor that is selected to prevent overdriving the crystal. It is not often needed if gain (Clock mode), C1 and C2 are selected properly. If the circuit is being overdriven and a lower gain Clock mode cannot be selected, then adding impedance with RS can decrease gain. This ...


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The diode in this circuit does not "achieve modulation". It's functioning as a "clamp" or "DC restoration" function so that the varying amplitude of the video does not affect the overall brighness in an objectionable way. It serves to keep the tips of the sync pulses (the most negative voltage within the composite video signal, corresponding to maximum RF ...


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for dt= C*dV / Ic for the Cap step response time initially then exponential decay. R divider ratio = k = 1/2 in this example dV = 2k * |Vo (max)| = |Vo_max| is the triangle swing to the comparator Vpp dt = T = RC = 1/2f = the triangle ramp time only for 64% asymptote and not k=1/2 of the Vmax output. C is the capacitor value thus you can compute T. ...


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Ouch! The opamp is used in non-linear mode. Linear opamp circuit calculation practices nor transfer functions are not applicable for it. You should divide this to a Schmitt-trigger and a charging and discharging RC circuit. Then you can find how long it takes for the RC circuit to charge and discharge between the tresholds of the Schmitt-trigger. ADD you ...


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Figure 3-4 is showing an oscillator instead of a crystal. The XO pin on the PHY is meant to provide an excitation source for a crystal located close to the IC. However, an oscillator contains this excitation source along with other circuitry to stabilize it and provide an output clock. Connect this output to both the PHY's XI pin and the MAC's REF_CLK pin. ...


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Most MCU datasheets and application notes do list some limits for the crystal, the loading capacitors, or at least they list some oscillator parameters to work with. For instance the STM32 application note you mentioned shows how to calculate if the crystal is compatible or not. If it is not compatible, try another crystal, perhaps with smaller frequency, ...


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Eric Vittoz was the analog IC designer who brought nanoWatt crystal oscillator methods to the Swiss watch industry. As part of that research effort, he published a paper on "too high a gain in the amplifier will prevent crystal/circuit oscillation", where the math shows root-locus plots at high transconductances crossing the ZERO phaseshift axis, quelling ...


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If it is really that hard to gauge correctly, why don't manufacturers provide better guidance? Oscillator designers have a tough job accommodating resonators over a very wide frequency range, and whose power-handling might range from fractions-of-microwatts to milliwatts. The oscillator driver runs in its linear region - a no-no for digital CMOS devices. ...


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A fractional frequency divider is rarely used by itself to provide a divided-down output. Although the divider you describe would on average produce an f0/2.5 signal, such a signal is rarely useful due to the large amount of jitter it has on it, as edges on the output signal obviously have to align with input signal edges. Instead, a fractional divider is ...


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The damping ratio \$\zeta\$ (zeta) of a \$RLC\$ filter can be evaluated using the logarithmic decrement \$\delta\$ (delta): \$\delta=ln(\alpha)=\frac{2\pi}{\sqrt{4Q^2-1}}\$ from which you extract \$Q\$ or \$\zeta\$ as detailed in the book I published on loop control: \$\zeta = \frac{1}{\sqrt{(\frac{2\pi}{\delta})^2+1}}\$. Let's see a practical application ...


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If you are familiar with the question 'an opamp has zero voltage between the input pins, so how can it produce an output?', then you have the answer. A PLL is a feedback system, with infinite gain at DC, large gain well below the loop bandwidth, gains around unity around the loop bandwidth (in fact unity gain defines the loop bandwidth, the loop filter ...


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The output of the phase comparator is the same : the output of the "loop filter" is not. To achieve zero phase error, you need infinite gain at zero frequency; i.e. a component of the loop filter is an integrator. An easier way to think of the loop filter, in this case, is as a PI controller, with the P (Proportional) term providing fast tracking of phase ...


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I tried the same circuit with 2N2222 (not 2N2222A) it did not work. Then I measured the voltage across the capapacitor, it was not rising more than 8.8 volts with source voltage at 14 volts. I disconnected emitter lead and voltage went up, that means the voltage leaked through transistor and did not allow to rise to expected level across the capacitor. I ...


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This would be a very good circuit to simulate. Often oscillators need a 'kick' to get them started, and a step on the power supply usually does it. Plot the currents vs. time and you'll see the behavior in start-up vs. steady-state is somewhat different.


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Before detailing my answer, I want to stress the fact that we are dealing with large signal circuits, therefore it is no more possible to model the MOSFET as a simple voltage controlled current generator with the capacity of sourcing and sinking any amount of current: in this context, its behavior is more similar to a switch that sinks current from a ...


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