Voltage controlled oscillator question

[John Fields]

On Fri, 14 May 2010 06:01:14 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

On May 13, 9:50 am, John Fields <jfie...@austininstruments.com> wrote:

news:t6piu55sqenrovms7k5fuhrl8m7666thng@4ax.com

from TI's 1989 GMOS logic data book.

Also, for an HC00, tpd at 25C is 15ns max for Vcc = 6V, 18ns for 4.5V,
and 90ns for 2V.- Hide quoted text -

- Show quoted text -

Hi John, You posted that link before, but I can't seem to make it
work. Is this on TI's web site?

---
No, it's on USENET at alt.binaries.schematics.electronic, which Google
groups can't access, and Verizon shut down access to the alt hierarchy
in July of last year, I think. AFAIK they may not even offer any
access to USENET any more.

If you want to get USENET directly and not through a web interface
like Google groups, then you need to get a USENET ISP and access
USENET with a newsreader.
---

It sounds like this would make an 'OK' VCO. And one could add some
outer control loop that would switch in (or out) two more inverters if
the control voltage got near the end of it's range. (As someone
already suggested.)

---
I'm not a big fan of that circuit, but just posted it to prove a
point.

BTW, I'll email you a copy of the PDF...

 

[George Herold]

On May 13, 9:50 am, John Fields <jfie...@austininstruments.com> wrote:

On Wed, 12 May 2010 22:07:32 -0500, "k...@att.bizzzzzzzzzzzz"





k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 12 May 2010 19:09:42 -0500, John Fields
jfie...@austininstruments.com> wrote:

On Tue, 11 May 2010 20:39:37 -0700 (PDT), Daku <dakup...@gmail.com
wrote:

Dear Sir,
I do not intend to use a ring oscillator based VCO.
However, as you have said below, literature search
shows a lot of people using the ring oscillator based
voltage controlled oscillator in phase locked loop
designs, which is sounds strange to me, since in a
phase locked loop, the VCO oscillation frequency
must be very sensitive to the input voltage level.
Maybe the ring oscillator is designed to oscillate
at the central frequency, but frequency variation is
difficult and tricky.

---
Please bottom post, or inline post when it's necessary for clarity.
Thank you.

As others have noted, your original post seems to indicate that you
don't have a really good grasp on what's required to change the
frequency of an oscillator as a function of an applied voltage.

For an LC tank, where:

              1
    f = -------------,
         2pi sqrt LC

then either L or C must be varied as a function of voltage in order to
make f change.

In the old days it was done with a saturable reactor, where the DC
voltage on the control winding and the attendant current through it
changed the reluctance of the core and, thererfore, the inductance
described by the secondary.

Today, afaik, it's done with varactors.

Comment?

It can be done with ring oscillators, too.  Gate delay isn't a strong function
of Vcc, though so it's not done often.  DLLs generally use a mux to select the
number of gates in the ring.

---
Actually, the change in delay is quite pronounced, as shown by:

news:t6piu55sqenrovms7k5fuhrl8m7666thng@4ax.com

from TI's 1989 GMOS logic data book.

Also, for an HC00, tpd at 25C is 15ns max for Vcc = 6V, 18ns for 4.5V,
and 90ns for 2V.- Hide quoted text -

- Show quoted text -

Hi John, You posted that link before, but I can't seem to make it
work. Is this on TI's web site?

It sounds like this would make an 'OK' VCO. And one could add some
outer control loop that would switch in (or out) two more inverters if
the control voltage got near the end of it's range. (As someone
already suggested.)


George H.

 

[Michael A. Terrell]

John Fields wrote:

No, it's on USENET at alt.binaries.schematics.electronic, which Google
groups can't access, and Verizon shut down access to the alt hierarchy
in July of last year, I think. AFAIK they may not even offer any
access to USENET any more.

If you want to get USENET directly and not through a web interface
like Google groups, then you need to get a USENET ISP and access
USENET with a newsreader.

<http://www.usenet-replayer.com/groups/alt.binaries.schematics.electronic.html>
archives some messages to ABSE, but I don't see that one.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[George Herold]

On May 14, 9:41 am, John Fields <jfie...@austininstruments.com> wrote:

On Fri, 14 May 2010 06:01:14 -0700 (PDT), George Herold

ggher...@gmail.com> wrote:
On May 13, 9:50 am, John Fields <jfie...@austininstruments.com> wrote:
news:t6piu55sqenrovms7k5fuhrl8m7666thng@4ax.com

from TI's 1989 GMOS logic data book.

Also, for an HC00, tpd at 25C is 15ns max for Vcc = 6V, 18ns for 4.5V,
and 90ns for 2V.- Hide quoted text -

- Show quoted text -

Hi John,  You posted that link before, but I can't seem to make it
work.  Is this on TI's web site?

---
No, it's on USENET at alt.binaries.schematics.electronic, which Google
groups can't access, and Verizon shut down access to the alt hierarchy
in July of last year, I think.  AFAIK they may not even offer any
access to USENET any more.

If you want to get USENET directly and not through a web interface
like Google groups, then you need to get a USENET ISP and access
USENET with a newsreader.
---

It sounds like this would make an 'OK' VCO.  And one could add some
outer control loop that would switch in (or out) two more inverters if
the control voltage got near the end of it's range.  (As someone
already suggested.)

---
I'm not a big fan of that circuit, but just posted it to prove a
point.

BTW, I'll email you a copy of the PDF...

"BTW, I'll email you a copy of the PDF..."

Wow thanks John! gherold@teachspin.com
I'm not planning on building anything, but it would be nice to see how
someone else did it.

George H.