better 4046 PLL

In a vague sort of way >:-} ...Jim Thompson

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R> >

I think it's you that is being vague here! :)

I am saying that if the input is a charge or current, the (fet) opamp will integrate it and there will be no error due to the virtual ground "bouncing around". Even if it is nominally far too slow for the input signals, it can still integrate them.

But if it is configured with an input resistor and used as a voltage integrator (rather than as a charge integrator) - then there will be errors due to the virtual ground moving.

--

John Devereux

< A 4046 or HC4046 could multiply by 5 to 200K, then we could divide by < 2 to 100K. That would use the drecky 4046 VCO and the drekkier phase < detector with tons of phase noise. Is there a better 4046 chip around, < or some equivalently simple pll/vco chip?

I'll bite. Is it possible to use a TL494? I only have one and have never used it. Seems like it could be a PLL. I only have seen one 565 in my life and it's currently being used in circuit so I can't really play with it too much.

The (x)nor gates in the 4046 never seemed right to me, but then again I still struggle with open -collector inputs for 74LS00P (I just learned about positive logic gates?!)

A pll tracking at megahertz(s) just seems frightening to one who doesn't have an HP or tecktronics scope.

anywise, maybe someone will know...

< The parameters for each device are brought out to a spice directive. You < can edit the D-flop and NAND speed, and the Gain, Bandwidth and Slew Rate < of the op amp by clicking on the desired directive and editing it.

Please, not again... How many changes can you make to a nand gate?

< You can see what happens when you change the width of the UP and DOWN < pulses by changing the NAND delay. In this circuit, yu will see it has < little effect on the op amp response since the UP and DOWN currents < cancel each other during the overlap time.

Where do you get your hardware?

< Changing the bandwidth and/or slew rate of the op amp can have a dramatic < effect on the response around zero.

I though that op amps where not supposed to have drastic effects.

< You can add the op amp of your choice and see how it responds to the < narrow pulses around zero. [I wish I had that kind of hardware.]

And again, I'm just learning about digital logic, please have some mercy on my posts ...