alternate active all-pass

[bitrex]

On 4/27/19 7:42 PM, Phil Hobbs wrote:

On 4/26/19 5:52 PM, Winfield Hill wrote:
bitrex wrote...

The perfectionist-man part of me wanted to continue however the
business/family man part of me successfully overruled and I ceased
labor immediately and had a relaxing weekend with the girl friend
instead.

Well it feels good to do math sometimes so I'll see what this idea
looks like out of curiosity. also she's away so I can get away
with it. Heh she probably worries I'm gonna go out on the town lol

  If you work on it and get her used to the idea that you
  need a little time for an outside affair, not to worry
  about it, you'll have plenty of free time for the lab.



Reminds me of an old joke.

Three friends, a doctor, a lawyer, and a physicist, were out having a
few drinks.  The topic came up: would you rather have a wife or a mistress?

The doctor said, "A wife for me, all the way.  I get called out at all
hours, even during holidays.  A mistress would never put up with that."

The lawyer said, "Are you nuts?  A wife can take you for all you've got.
 A mistress for me any day."

The physicist said, "I'd like both."

The others replied, "Both?  Why?"

The physicist replied, "Well, with both, if I tell the mistress that I'm
with the wife, and I tell the wife that I'm with the mistress, I can
spend my time at the lab!"

Boom-tsssh.

Cheers

Phil Hobbs

Since rovin's been my ru-eye-in

<https://www.youtube.com/watch?v=b2JO-i2aPs8>

 

Phil Hobbs wrote:

Reminds me of an old joke.

Three friends, a doctor, a lawyer, and a physicist, were out having a
few drinks. The topic came up: would you rather have a wife or a mistress?

The doctor said, "A wife for me, all the way. I get called out at all
hours, even during holidays. A mistress would never put up with that."

The lawyer said, "Are you nuts? A wife can take you for all you've got.
A mistress for me any day."

The physicist said, "I'd like both."

The others replied, "Both? Why?"

The physicist replied, "Well, with both, if I tell the mistress that I'm
with the wife, and I tell the wife that I'm with the mistress, I can
spend my time at the lab!"

Boom-tsssh.

** The "spherical chickens in a vacuum" joke from the Big Bang Theory is a lot funnier.

https://www.youtube.com/watch?v=StHMKdvuHN0



...... Phil

 

[Tom Gardner]

On 28/04/19 00:42, Phil Hobbs wrote:

On 4/26/19 5:52 PM, Winfield Hill wrote:
bitrex wrote...

The perfectionist-man part of me wanted to continue however the
business/family man part of me successfully overruled and I ceased
labor immediately and had a relaxing weekend with the girl friend
instead.

Well it feels good to do math sometimes so I'll see what this idea
looks like out of curiosity. also she's away so I can get away
with it. Heh she probably worries I'm gonna go out on the town lol

  If you work on it and get her used to the idea that you
  need a little time for an outside affair, not to worry
  about it, you'll have plenty of free time for the lab.



Reminds me of an old joke.

Three friends, a doctor, a lawyer, and a physicist, were out having a few
drinks.  The topic came up: would you rather have a wife or a mistress?

The doctor said, "A wife for me, all the way.  I get called out at all hours,
even during holidays.  A mistress would never put up with that."

The lawyer said, "Are you nuts?  A wife can take you for all you've got.  A
mistress for me any day."

The physicist said, "I'd like both."

The others replied, "Both?  Why?"

The physicist replied, "Well, with both, if I tell the mistress that I'm with
the wife, and I tell the wife that I'm with the mistress, I can spend my time at
the lab!"

Boom-tsssh.

I always heard that with engineers, not physicists.

The old ones are the best, of course.

 

[bitrex]

On 4/28/19 4:13 PM, John Larkin wrote:

On Sun, 28 Apr 2019 12:50:22 -0700 (PDT), gyansorova@gmail.com wrote:

On Saturday, April 27, 2019 at 4:01:19 AM UTC+12, John Larkin wrote:
The classic opamp all-pass is in Williams 3,

https://www.dropbox.com/s/nhevg979w7gtxib/90_degree.JPG?dl=0

We're doing that but see some harmonic distortion at high frequency,
above 8 MHz in our case. This circuit inverts at low frequencies and
has unity gain at high frequency. Opamps have bad CMRR at high
frequencies, which is why Jim Williams said "always invert."

There could also be some problems from the finite output impedance of
each opamp driving the next stage, which sort of differentiates its
output. Our resistances are getting pretty low.

Wouldn't this work?

https://www.dropbox.com/s/jj9f3kp0svar7rw/Alt_All-Pass.JPG?dl=0

Circuit B is an inverter at high frequencies, unity gain at low. Gotta
try that. We'd just swap some parts on the board and redefine some
phase conventions.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nowadays though would we even bother. Do everything with DSP where possible unless the frequency is beyond it.

We're doing an all analog I/Q modulator box to simulate an
eddy-current transducer, 1-30 MHz range. It's a starter project for a
new engineer.

well let him figure out what all-pass filter to use then, mr. mom!!!

 

[John Larkin]

On Sun, 28 Apr 2019 12:50:22 -0700 (PDT), gyansorova@gmail.com wrote:

On Saturday, April 27, 2019 at 4:01:19 AM UTC+12, John Larkin wrote:
The classic opamp all-pass is in Williams 3,

https://www.dropbox.com/s/nhevg979w7gtxib/90_degree.JPG?dl=0

We're doing that but see some harmonic distortion at high frequency,
above 8 MHz in our case. This circuit inverts at low frequencies and
has unity gain at high frequency. Opamps have bad CMRR at high
frequencies, which is why Jim Williams said "always invert."

There could also be some problems from the finite output impedance of
each opamp driving the next stage, which sort of differentiates its
output. Our resistances are getting pretty low.

Wouldn't this work?

https://www.dropbox.com/s/jj9f3kp0svar7rw/Alt_All-Pass.JPG?dl=0

Circuit B is an inverter at high frequencies, unity gain at low. Gotta
try that. We'd just swap some parts on the board and redefine some
phase conventions.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nowadays though would we even bother. Do everything with DSP where possible unless the frequency is beyond it.

We're doing an all analog I/Q modulator box to simulate an
eddy-current transducer, 1-30 MHz range. It's a starter project for a
new engineer.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Saturday, April 27, 2019 at 4:01:19 AM UTC+12, John Larkin wrote:

The classic opamp all-pass is in Williams 3,

https://www.dropbox.com/s/nhevg979w7gtxib/90_degree.JPG?dl=0

We're doing that but see some harmonic distortion at high frequency,
above 8 MHz in our case. This circuit inverts at low frequencies and
has unity gain at high frequency. Opamps have bad CMRR at high
frequencies, which is why Jim Williams said "always invert."

There could also be some problems from the finite output impedance of
each opamp driving the next stage, which sort of differentiates its
output. Our resistances are getting pretty low.

Wouldn't this work?

https://www.dropbox.com/s/jj9f3kp0svar7rw/Alt_All-Pass.JPG?dl=0

Circuit B is an inverter at high frequencies, unity gain at low. Gotta
try that. We'd just swap some parts on the board and redefine some
phase conventions.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nowadays though would we even bother. Do everything with DSP where possible unless the frequency is beyond it.

 

[John Larkin]

On Sun, 28 Apr 2019 16:38:13 -0400, bitrex <user@example.net> wrote:

On 4/28/19 4:13 PM, John Larkin wrote:
On Sun, 28 Apr 2019 12:50:22 -0700 (PDT), gyansorova@gmail.com wrote:

On Saturday, April 27, 2019 at 4:01:19 AM UTC+12, John Larkin wrote:
The classic opamp all-pass is in Williams 3,

https://www.dropbox.com/s/nhevg979w7gtxib/90_degree.JPG?dl=0

We're doing that but see some harmonic distortion at high frequency,
above 8 MHz in our case. This circuit inverts at low frequencies and
has unity gain at high frequency. Opamps have bad CMRR at high
frequencies, which is why Jim Williams said "always invert."

There could also be some problems from the finite output impedance of
each opamp driving the next stage, which sort of differentiates its
output. Our resistances are getting pretty low.

Wouldn't this work?

https://www.dropbox.com/s/jj9f3kp0svar7rw/Alt_All-Pass.JPG?dl=0

Circuit B is an inverter at high frequencies, unity gain at low. Gotta
try that. We'd just swap some parts on the board and redefine some
phase conventions.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nowadays though would we even bother. Do everything with DSP where possible unless the frequency is beyond it.

We're doing an all analog I/Q modulator box to simulate an
eddy-current transducer, 1-30 MHz range. It's a starter project for a
new engineer.


well let him figure out what all-pass filter to use then, mr. mom!!!

Certain Parties talked me into using wideband all-pass shifters and
some other cute tricks. It was pretty much a disaster. So on Friday we
decided to go maximally simple and just get it done.

https://www.dropbox.com/s/h37vfbv0cjt6ybc/90_deg_allpass_1.jpg?dl=0

I hate it when we mess up the rev A board. Well, it was his first
project, with a lot to learn.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[bitrex]

On 4/28/19 9:35 PM, John Larkin wrote:

On Sun, 28 Apr 2019 16:38:13 -0400, bitrex <user@example.net> wrote:

On 4/28/19 4:13 PM, John Larkin wrote:
On Sun, 28 Apr 2019 12:50:22 -0700 (PDT), gyansorova@gmail.com wrote:

On Saturday, April 27, 2019 at 4:01:19 AM UTC+12, John Larkin wrote:
The classic opamp all-pass is in Williams 3,

https://www.dropbox.com/s/nhevg979w7gtxib/90_degree.JPG?dl=0

We're doing that but see some harmonic distortion at high frequency,
above 8 MHz in our case. This circuit inverts at low frequencies and
has unity gain at high frequency. Opamps have bad CMRR at high
frequencies, which is why Jim Williams said "always invert."

There could also be some problems from the finite output impedance of
each opamp driving the next stage, which sort of differentiates its
output. Our resistances are getting pretty low.

Wouldn't this work?

https://www.dropbox.com/s/jj9f3kp0svar7rw/Alt_All-Pass.JPG?dl=0

Circuit B is an inverter at high frequencies, unity gain at low. Gotta
try that. We'd just swap some parts on the board and redefine some
phase conventions.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nowadays though would we even bother. Do everything with DSP where possible unless the frequency is beyond it.

We're doing an all analog I/Q modulator box to simulate an
eddy-current transducer, 1-30 MHz range. It's a starter project for a
new engineer.


well let him figure out what all-pass filter to use then, mr. mom!!!

Certain Parties talked me into using wideband all-pass shifters and
some other cute tricks. It was pretty much a disaster. So on Friday we
decided to go maximally simple and just get it done.

Since the active all-passer only needs a fast buffer and it sees a
purely resistive Z at it's non-inverting terminal a current-feedback amp
might be a better choice

https://www.dropbox.com/s/h37vfbv0cjt6ybc/90_deg_allpass_1.jpg?dl=0

I hate it when we mess up the rev A board. Well, it was his first
project, with a lot to learn.

Lots of phase-shifting circuits "in the literature" (this is circa
1950.) Hey a circular sweep generator have him design one of those!
Sounds like fun!

<https://www.dropbox.com/s/iqd0l9jht1fcoe3/IMG_20190428_222418717_HDR.jpg?dl=0>