Driver to drive?

On Sunday, March 26, 2017 at 11:24:24 AM UTC+11, k...@notreal.com wrote:

On Sat, 25 Mar 2017 14:34:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/23/2017 12:45 PM, krw@notreal.com wrote:
On Thu, 23 Mar 2017 06:42:31 -0000, "Kevin Aylward"
kevinRemovAT@kevinaylward.co.uk> wrote:

wrote in message news:0v46dc9bgb5pjf6lpc3jej19tl97qpu4db@4ax.com...

model, Jesus, emphatically instructing them that "thou shall not kill".
More, stunningly the xtians claim that it is they that there the
morally
righteous ones.

The perp gave up his right to life by taking that of another. End of
story.

Ok. After the Jury, judge and executioners have killed the
aforementioned,
we can now kill said Jury, judge and executioners because they have now
killed someone, or taken deliberate action that resulted in the death of
someone. i.e. murdered someone.

It's obvious you're illiterate.

Its obvious that you can't understand the issues involved.



Ho humm.

OK, you're not interested in the facts. Therefore, the only
conclusion possible is that you're trolling. Meet Slowman.

I gave you facts.

No, you don't even know the difference (I didn't read after your first
lie).

Well, there you go. It's pretty hard to have a conversation with
someone who isn't even going to listen to what you say. "Don't bother
me with the facts!"

That's *exactly* the point, moron. If the other person is lying,
there is no intention of having a conversation. It's the favorite
tool of you lefties.

Krw's definition of a lie is something he disagrees with. Appreciating this point makes his posts more understandable, though not a jot more useful.

--
Bill Sloman, Sydney

 

[rickman]

On 3/25/2017 6:25 PM, dagmargoodboat@yahoo.com wrote:

On Saturday, March 25, 2017 at 3:20:31 PM UTC-4, rickman wrote:
On 3/25/2017 2:33 PM, dagmargoodboat@yahoo.com wrote:

Summary:
o The FET-as-voltage follower has a gain of 0.98, which is quite
decent for our purposes.
o Input capacitance is 1.2pF.
o We've reduced the input capacitance by a factor of about 4 compared
to Kleijer, but it's still not as low as expected.

The shield driver + BNC isn't going to work, not until we get the gain closer
to 1, rather than 0.25.

The gain of 0.25 is not because of the voltage follower, it's from the
series cap.

The net gain's a result of the *divider* formed by the series coupling cap
and (the FET input capacitance + strays), multiplied by the follower gain.
I asked Mike to measure the follower gain so we could then calculate the
input capacitance.

Yes, of course, but the lost voltage is across the input cap. The
voltage follower gain will be nearly 1 in all variations. The
capacitance of the amp input is a function of it's intrinsic capacitance
and the gain. Closer to 1 the gain is the smaller the bootstrap makes
the effective input capacitance.

Are you suggesting you can get the amp input capacitance
down to 10x less than the series cap?

Bootstrapping should reduce the FET input capacitance by a factor of
1/(1-G), where G = the gain of the bootstrap.

That's not what I asked. What is important in determining the circuit
gain is the amp's effective capacitance value compared to the input cap.
To get the gain of the input amp with input cap close to 1, the
effective input capacitance of the amp would need to be ball park 10
times lower than the input cap.

If the gain of the input amp were made more than 1, (to compensate for
the lost gain in the cap divider) the circuit could easily become
unstable. A follower won't have gain of 1 or more, only approach 1.

I don't know how close you can get to a gain of 1 for the amp and input
cap, but I think it will be hard to get the amp effective input
capacitance anywhere near 0.04 pf. If you can do that, you really don't
need the input cap. I believe it's purpose was to mitigate the input
capacitance of the amp so it didn't impact the circuit being measured.
If you can get the amp effective input capacitance below 0.4 pF, you can
do away with the input cap and it's voltage division.

Remember what the input cap is for. That's why I suggested it might be
useful to put it in the probe end. Using a coax with the shield as
guard, there should be little problem with noise. Heck, you are
measuring antennas/coils. Kleijer found a radio station in his
measurements because the coil was picking it up.

Another approach would be to put the series cap outside the box in the
probe tip as is done in o'scopes. Then the gain of the amp would be
sufficient to tie the coax shield to the output of the amp.

That's true. Mike could use a shielded connector and cable if he didn't
mind putting his series cap at the probe.

What level do you think the amp input capacitance can reach?

Down to the strays, if we want, or even less. See above. This circuit
should be under 1/2 pF, by my estimate.

Cheers,
James Arthur

Based on your report I think the culprit limiting our improvement is likely
the drain driver, Q1 and related components. If you could 'scope (A) and
(B), a.c.-coupled, with the 'scope set to subtract the two channels,
(A)-(B) would tell us if our drain bootstrap is up to snuff.

I might have to cobble one of these together so I can probe it myself...

Nice work Mike. You've made something that's 4x better, even as it is.

Cheers,
James Arthur

+12V +12V
-+- -+-
| |
| [22k] R5
Q1 \| | 8.0v
BC547B |---+-------.
7.4v .<| | | input 1Vpp
| | | T1s 0.25Vpp
(B)| [47k] R6 | output 0.24Vpp
(shield) T1 |--' | |
----- BF256C | === |
----------||-+----->|--. |
---+- .4pF| (A)| Vdd --- C2
| | | -+- ---100n
| | | | |
| R1 [10M] | |/ Q2 |
| | 3.4v +---| BC547B |
| | | |>. |
| | R3 [470] |2.7v |
| | | | | C3
| | | | (C)| 100n
| +----||---+-----+-------+-----||---> to ampl.
| | C1 | |
| R2 [10M] 100pF R4 [470] --- C4
| | | --- 100n
| === === |
| |
'------------------------------+
|
Cin ~200fF [2.2k] R7
|
===

--

Rick C

 

On Sunday, March 26, 2017 at 11:25:22 AM UTC+11, k...@notreal.com wrote:

On Sat, 25 Mar 2017 19:37:17 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 25 Mar 2017 18:05:27 +0000, Kevin Aylward wrote:

I may not always agree with Bill, but I have never seen any evidence
that Bill lies.

boggle

Either Kevin is dumber than a stump, a troll, or liar. Perhaps all
three.

There is another option which is that krw is just as dumb as a stump, in that he can't process new information, let alone use it to correct his numerous misapprehensions. It's a whole lot more plausible than the proposition the Kevin Aylward is dumb or deceitful. Kevin does have his own collection of misapprehensions, but it's a lot smaller than krw's.

--
Bill Sloman, Sydney

 

[amdx]

On 3/25/2017 6:00 PM, dagmargoodboat@yahoo.com wrote:

On Saturday, March 25, 2017 at 3:44:39 PM UTC-4, amdx wrote:
On 3/25/2017 1:33 PM, dagmargoodboat@yahoo.com wrote:

Based on your report I think the culprit limiting our improvement is likely
the drain driver, Q1 and related components. If you could 'scope (A) and
(B), a.c.-coupled, with the 'scope set to subtract the two channels,
(A)-(B) would tell us if our drain bootstrap is up to snuff.

I might have to cobble one of these together so I can probe it myself...

Nice work Mike. You've made something that's 4x better, even as it is.


I adjusted both probes to be flat, then I connected both probes to the
same point (T1d) and adjusted *Var. for exact overlay of the two
waveforms. Then I move one probe to (T1s), I can not see any difference
in the signals.They still overlay, maybe a little thicker trace. I have
the brightness turned way down to make a thin trace, focus adjusted.
Looking for any small difference.

I'm a little confused by my scope. There is not a clear subtract (A-B).

The manual says ADD then INVERT to get a difference**.
See page 3-5 in the manual.
https://www.scribd.com/document/25186404/Tektronix-2465B-Options-and-Operator-Manual
Following the method in the manual, I get about 4mV of difference signal.
If this is not satisfactory, I have another Tektronix scope (475), I
can put on the bench. I think that has subtract.

* this was a very minor tweak
** this seems a poor method if your wave form is slightly asymmetrical.
But I don't see that.
Mikek

That's good technique, but the result is a little puzzling--with
bootstrapping gain this close to unity we'd expect better cancellation
of the FET capacitances.

The FET-follower into a current-sink load has a gain of 0.98 (measured).
That should cancel 98% of Cgs, the largest FET capacitance (5pF).

The drain-follower circuit also has a gain of roughly
(250mV-4mV)/250mV = .98, which, following the .98 gain of the FET stage,
produces a drain bootstrap gain of 0.96. That should cancel 96% of the
BF256C's Cdg (1.2pF), the remaining input-related capacitance.

Either there's close to 1pF of stray capacitance to ground at the input
node, or ... I've missed something. Like, what's your test frequency?
I've been assuming 1MHz (crystal-radio band).

Cheers,
James Arthur

Yes, 1 MHZ.
I've checked my circuit layout many times, But still, any
thing that could be wrong to cause this?
I'll go check resistor values while waiting for a response,
maybe I got two of them reversed, I don't expect it though.
Thanks, Mikek

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[rickman]

On 3/25/2017 7:27 PM, amdx wrote:

On 3/25/2017 6:00 PM, dagmargoodboat@yahoo.com wrote:
On Saturday, March 25, 2017 at 3:44:39 PM UTC-4, amdx wrote:
On 3/25/2017 1:33 PM, dagmargoodboat@yahoo.com wrote:

Based on your report I think the culprit limiting our improvement is
likely
the drain driver, Q1 and related components. If you could 'scope
(A) and
(B), a.c.-coupled, with the 'scope set to subtract the two channels,
(A)-(B) would tell us if our drain bootstrap is up to snuff.

I might have to cobble one of these together so I can probe it
myself...

Nice work Mike. You've made something that's 4x better, even as it is.


I adjusted both probes to be flat, then I connected both probes to the
same point (T1d) and adjusted *Var. for exact overlay of the two
waveforms. Then I move one probe to (T1s), I can not see any difference
in the signals.They still overlay, maybe a little thicker trace. I have
the brightness turned way down to make a thin trace, focus adjusted.
Looking for any small difference.

I'm a little confused by my scope. There is not a clear subtract
(A-B).

The manual says ADD then INVERT to get a difference**.
See page 3-5 in the manual.
https://www.scribd.com/document/25186404/Tektronix-2465B-Options-and-Operator-Manual

Following the method in the manual, I get about 4mV of difference
signal.
If this is not satisfactory, I have another Tektronix scope (475), I
can put on the bench. I think that has subtract.

* this was a very minor tweak
** this seems a poor method if your wave form is slightly asymmetrical.
But I don't see that.
Mikek

That's good technique, but the result is a little puzzling--with
bootstrapping gain this close to unity we'd expect better cancellation
of the FET capacitances.

The FET-follower into a current-sink load has a gain of 0.98 (measured).
That should cancel 98% of Cgs, the largest FET capacitance (5pF).

The drain-follower circuit also has a gain of roughly
(250mV-4mV)/250mV = .98, which, following the .98 gain of the FET stage,
produces a drain bootstrap gain of 0.96. That should cancel 96% of the
BF256C's Cdg (1.2pF), the remaining input-related capacitance.

Either there's close to 1pF of stray capacitance to ground at the input
node, or ... I've missed something. Like, what's your test frequency?
I've been assuming 1MHz (crystal-radio band).

Cheers,
James Arthur


Yes, 1 MHZ.
I've checked my circuit layout many times, But still, any
thing that could be wrong to cause this?
I'll go check resistor values while waiting for a response,
maybe I got two of them reversed, I don't expect it though.

If the resistor values were swapped the DC levels would be off. That's
what they are there for, to set the bias points. What's the DC level at
point (C) just before the output cap?

--

Rick C

 

[Kevin Aylward]

"Cursitor Doom" wrote in message newsb6gtd$rl8$1@dont-email.me...

On Sat, 25 Mar 2017 18:05:27 +0000, Kevin Aylward wrote:

I may not always agree with Bill, but I have never seen any evidence
that Bill lies.

boggle

https://www.youtube.com/watch?v=NX45hc0aZt0


-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

 

On Sat, 25 Mar 2017 14:19:36 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/24/2017 9:03 AM, Michael A. Terrell wrote:
krw@notreal.com wrote:
On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

That's impossible, which is the whole "reasonable" thing.

Nothing whatsoever impossible about it!

Not at all. There is always doubt. It may be an unreasonable doubt
but there is _always_ doubt (what if the Earth was really flat?).
Hence, "beyond reasonable doubt".


What do you think of this sorry piece of work?

http://www.wftv.com/news/local/ayala-to-explain-why-she-wont-seek-death-penalty-against-murder-suspect-markeith-loyd/503151996


She should *immediately* be removed from office for violating her oath
of office to follow the constitution and laws of the state of Florida.
That decision isn't hers to make.


The Governor has removed her from the case, but she want to sue over it.

Disbar the jackass.

What did she do wrong? It is in the prosecutor's domain to decide how
to prosecute a case. I haven't looked up the law, but I seriously doubt
it says the death penalty is mandatory in all cases.

Why don't you try reading instead of just firing form the lip.

 

On Sat, 25 Mar 2017 14:34:15 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/23/2017 12:45 PM, krw@notreal.com wrote:
On Thu, 23 Mar 2017 06:42:31 -0000, "Kevin Aylward"
kevinRemovAT@kevinaylward.co.uk> wrote:

wrote in message news:0v46dc9bgb5pjf6lpc3jej19tl97qpu4db@4ax.com...

model, Jesus, emphatically instructing them that "thou shall not kill".
More, stunningly the xtians claim that it is they that there the
morally
righteous ones.

The perp gave up his right to life by taking that of another. End of
story.

Ok. After the Jury, judge and executioners have killed the
aforementioned,
we can now kill said Jury, judge and executioners because they have now
killed someone, or taken deliberate action that resulted in the death of
someone. i.e. murdered someone.

It's obvious you're illiterate.

Its obvious that you can't understand the issues involved.



Ho humm.

OK, you're not interested in the facts. Therefore, the only
conclusion possible is that you're trolling. Meet Slowman.

I gave you facts.

No, you don't even know the difference (I didn't read after your first
lie).

Well, there you go. It's pretty hard to have a conversation with
someone who isn't even going to listen to what you say. "Don't bother
me with the facts!"

That's *exactly* the point, moron. If the other person is lying,
there is no intention of having a conversation. It's the favorite
tool of you lefties.

 

On Sat, 25 Mar 2017 19:37:17 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 25 Mar 2017 18:05:27 +0000, Kevin Aylward wrote:

I may not always agree with Bill, but I have never seen any evidence
that Bill lies.

boggle

Either Kevin is dumber than a stump, a troll, or liar. Perhaps all
three.

 

On Sat, 25 Mar 2017 14:20:46 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/25/2017 3:34 AM, Michael A. Terrell wrote:
Cursitor Doom wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time? We
have an overcrowding crisis right now because the system is clogged
up by 'bed-blockers' who could easily be removed at zero further cost
to the taxpayer.


Indeed. Give him life, and he'll file appeal after appeal, until he's
dead. It can run into millions of dollars.

I believe the cost of executing someone is even higher.

Utter nonsense. It's the appeal after appeal, until he's dead that's
the expensive part. There is absolutely *no* reason it should take 20
years.

 

On Sat, 25 Mar 2017 18:08:18 -0000, "Kevin Aylward"
<kevinRemovAT@kevinaylward.co.uk> wrote:

wrote in message news:s1tcdctmds0hl22fo9hpbh5enshegc86gm@4ax.com...

On Sat, 25 Mar 2017 03:32:41 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Kevin Aylward wrote:
wrote in message news:mnq8dcpnbekopn07j0cu3crq12hq0905l1@4ax.com...

On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

That's impossible, which is the whole "reasonable" thing.

Nothing whatsoever impossible about it!

Not at all. There is always doubt. It may be an unreasonable doubt
but there is _always_ doubt (what if the Earth was really flat?).
Hence, "beyond reasonable doubt".


What do you think of this sorry piece of work?

http://www.wftv.com/news/local/ayala-to-explain-why-she-wont-seek-death-penalty-against-murder-suspect-markeith-loyd/503151996


She should *immediately* be removed from office for violating her oath
of office to follow the constitution and laws of the state of Florida.
That decision isn't hers to make.

Ho hummm..

Like, what specific law says that anybody has to demand the death of
someone else? Dah....


It's her job tpoo follow the laws, not decide which ones she likes.
In that case, he murdered a police officer in front of a lot of people,

Please cite the exact law that says that a prosecutor must demand the death
penalty.

You don't read any better than Ricky.

 

[amdx]

On 3/25/2017 5:25 PM, dagmargoodboat@yahoo.com wrote:

On Saturday, March 25, 2017 at 3:20:31 PM UTC-4, rickman wrote:
On 3/25/2017 2:33 PM, dagmargoodboat@yahoo.com wrote:

Summary:
o The FET-as-voltage follower has a gain of 0.98, which is quite
decent for our purposes.
o Input capacitance is 1.2pF.
o We've reduced the input capacitance by a factor of about 4 compared
to Kleijer, but it's still not as low as expected.

The shield driver + BNC isn't going to work, not until we get the gain closer
to 1, rather than 0.25.

The gain of 0.25 is not because of the voltage follower, it's from the
series cap.

The net gain's a result of the *divider* formed by the series coupling cap
and (the FET input capacitance + strays), multiplied by the follower gain.
I asked Mike to measure the follower gain so we could then calculate the
input capacitance.

Are you suggesting you can get the amp input capacitance
down to 10x less than the series cap?

Bootstrapping should reduce the FET input capacitance by a factor of
1/(1-G), where G = the gain of the bootstrap.

Another approach would be to put the series cap outside the box in the
probe tip as is done in o'scopes. Then the gain of the amp would be
sufficient to tie the coax shield to the output of the amp.

That's true. Mike could use a shielded connector and cable if he didn't
mind putting his series cap at the probe.

The plan is to permanently wire the coax end to the tuning cap, and then
swap different coils to it.
I was about to say that a series cap at the probe not a good plan, but I
could put some type of permanent connection on my tuning cap to hold the
0.4pf cap and the connect the coax to that. I suspect I'd be adding
capacitance with that though.

What level do you think the amp input capacitance can reach?

Down to the strays, if we want, or even less. See above. This circuit
should be under 1/2 pF, by my estimate.

Cheers,
James Arthur

Based on your report I think the culprit limiting our improvement is likely
the drain driver, Q1 and related components. If you could 'scope (A) and
(B), a.c.-coupled, with the 'scope set to subtract the two channels,
(A)-(B) would tell us if our drain bootstrap is up to snuff.

I might have to cobble one of these together so I can probe it myself...

Nice work Mike. You've made something that's 4x better, even as it is.

Cheers,
James Arthur

+12V +12V
-+- -+-
| |
| [22k] R5
Q1 \| | 8.0v
BC547B |---+-------.
7.4v .<| | | input 1Vpp
| | | T1s 0.25Vpp
(B)| [47k] R6 | output 0.24Vpp
(shield) T1 |--' | |
----- BF256C | === |
----------||-+----->|--. |
---+- .4pF| (A)| Vdd --- C2
| | | -+- ---100n
| | | | |
| R1 [10M] | |/ Q2 |
| | 3.4v +---| BC547B |
| | | |>. |
| | R3 [470] |2.7v |
| | | | | C3
| | | | (C)| 100n
| +----||---+-----+-------+-----||---> to ampl.
| | C1 | |
| R2 [10M] 100pF R4 [470] --- C4
| | | --- 100n
| === === |
| |
'------------------------------+
|
Cin ~200fF [2.2k] R7
|
===

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[rickman]

On 3/25/2017 8:02 PM, dagmargoodboat@yahoo.com wrote:

On Saturday, March 25, 2017 at 7:18:00 PM UTC-4, rickman wrote:
On 3/25/2017 6:25 PM, dagmargoodboat@yahoo.com wrote:
On Saturday, March 25, 2017 at 3:20:31 PM UTC-4, rickman wrote:
On 3/25/2017 2:33 PM, dagmargoodboat@yahoo.com wrote:

Summary:
o The FET-as-voltage follower has a gain of 0.98, which is quite
decent for our purposes.
o Input capacitance is 1.2pF.
o We've reduced the input capacitance by a factor of about 4 compared
to Kleijer, but it's still not as low as expected.

The shield driver + BNC isn't going to work, not until we get the gain closer
to 1, rather than 0.25.

The gain of 0.25 is not because of the voltage follower, it's from the
series cap.

The net gain's a result of the *divider* formed by the series coupling cap
and (the FET input capacitance + strays), multiplied by the follower gain.
I asked Mike to measure the follower gain so we could then calculate the
input capacitance.

Yes, of course, but the lost voltage is across the input cap. The
voltage follower gain will be nearly 1 in all variations. The
capacitance of the amp input is a function of it's intrinsic capacitance
and the gain. Closer to 1 the gain is the smaller the bootstrap makes
the effective input capacitance.


Are you suggesting you can get the amp input capacitance
down to 10x less than the series cap?

Bootstrapping should reduce the FET input capacitance by a factor of
1/(1-G), where G = the gain of the bootstrap.

That's not what I asked. What is important in determining the circuit
gain is the amp's effective capacitance value compared to the input cap.
To get the gain of the input amp with input cap close to 1, the
effective input capacitance of the amp would need to be ball park 10
times lower than the input cap.

If the gain of the input amp were made more than 1, (to compensate for
the lost gain in the cap divider) the circuit could easily become
unstable. A follower won't have gain of 1 or more, only approach 1.

I don't know how close you can get to a gain of 1 for the amp and input
cap, but I think it will be hard to get the amp effective input
capacitance anywhere near 0.04 pf. If you can do that, you really don't
need the input cap. I believe it's purpose was to mitigate the input
capacitance of the amp so it didn't impact the circuit being measured.
If you can get the amp effective input capacitance below 0.4 pF, you can
do away with the input cap and it's voltage division.

Remember what the input cap is for. That's why I suggested it might be
useful to put it in the probe end. Using a coax with the shield as
guard, there should be little problem with noise. Heck, you are
measuring antennas/coils. Kleijer found a radio station in his
measurements because the coil was picking it up.


Another approach would be to put the series cap outside the box in the
probe tip as is done in o'scopes. Then the gain of the amp would be
sufficient to tie the coax shield to the output of the amp.

That's true. Mike could use a shielded connector and cable if he didn't
mind putting his series cap at the probe.

What level do you think the amp input capacitance can reach?

Down to the strays, if we want, or even less. See above. This circuit
should be under 1/2 pF, by my estimate.

Cheers,
James Arthur

Based on your report I think the culprit limiting our improvement is likely
the drain driver, Q1 and related components. If you could 'scope (A) and
(B), a.c.-coupled, with the 'scope set to subtract the two channels,
(A)-(B) would tell us if our drain bootstrap is up to snuff.

I might have to cobble one of these together so I can probe it myself...

Nice work Mike. You've made something that's 4x better, even as it is.

Cheers,
James Arthur

+12V +12V
-+- -+-
| |
| [22k] R5
Q1 \| | 8.0v
BC547B |---+-------.
7.4v .<| | | input 1Vpp
| | | T1s 0.25Vpp
(B)| [47k] R6 | output 0.24Vpp
(shield) T1 |--' | |
----- BF256C | === |
----------||-+----->|--. |
---+- .4pF| (A)| Vdd --- C2
| | | -+- ---100n
| | | | |
| R1 [10M] | |/ Q2 |
| | 3.4v +---| BC547B |
| | | |>. |
| | R3 [470] |2.7v |
| | | | | C3
| | | | (C)| 100n
| +----||---+-----+-------+-----||---> to ampl.
| | C1 | |
| R2 [10M] 100pF R4 [470] --- C4
| | | --- 100n
| === === |
| |
'------------------------------+
|
Cin ~200fF [2.2k] R7
|
===



--

Rick C

I think you might want to re-read the thread. With a low Cin(eff),
net gain should be close to unity, *including* the coupling cap.

I never said that wasn't true. My point is that to get close to unity
including the input cap, the effective input capacitance of the
amplifier has to be *much* lower than the input cap. At that point, why
*have* the input cap? Is there DC to be blocked? In fact, at that
point the input cap could be replaced with a much larger value since its
value no longer determines the circuit input capacitance.

Wasn't that the reason the input cap is in the circuit, to reduce the
input capacitance of the circuit exactly like the 10x dividing resistor
in an oscilloscope probe raises the input resistance of the scope?

--

Rick C

 

[Jasen Betts]

On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:

On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it ws cheaper than death row.

We have
an overcrowding crisis right now because the system is clogged up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs
--
This email has not been checked by half-arsed antivirus software

 

On Sunday, March 26, 2017 at 5:30:48 PM UTC+11, John Robertson wrote:

On 2017/03/25 6:26 PM, Jasen Betts wrote:
On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it ws cheaper than death row.


We have
an overcrowding crisis right now because the system is clogged up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs


Part of the problem appears to be that the USA locks up more people per
capita than any other developed nation.

Why?

It's been looked at, and the main difference seems to be longer sentences in the US, rather than a more criminal population. The sample of the US population that posts here doesn't seem to be representative.

--
Bill Sloman, Sydney

 

[John Robertson]

On 2017/03/25 6:26 PM, Jasen Betts wrote:

On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it ws cheaper than death row.


We have
an overcrowding crisis right now because the system is clogged up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs

Part of the problem appears to be that the USA locks up more people per
capita than any other developed nation.

Why?

John

 

[Sylvia Else]

On 26/03/2017 4:33 PM, John Larkin wrote:

On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

I'm using this circuit to provide 250V pulses to an ignition coil.

https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0

The IC is a Linear Technology LT1243.

12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3
is ground.

LTSpice says that this works, and indeed the real implementation does.
Mostly.

The difference is that after the circuit has been triggered once, it
won't charge the capacitor again (above about 25 volts) for a varying
period that can be up to half a minute. It's as if the wrong level is
being used internally to compare with the feedback pin. In that regard,
I'll mention that Q3 is used to pull FB up so that the circuit stops
driving the FET, since otherwise the SCR never turns off. I've checked,
and the problem is not that Q3 remains on, nor is it that the SCR fails
to turn off. In any case, the 1.5uF capacitor C1 does get charged
somewhat, as I mentioned above.

When the issue resolves, it does so rapidly, within a fraction of a second.

Connecting an oscilloscope probe to the RT/CT pin of the IC restores
function, but only if the scope is set to DC coupling - not AC coupling
- and functioning continues only as long as the probe remains connected
- until the aforesaid varying period has elapsed. Touching the pin with
a finger has a similar effect.

That is, connect probe; works. Disconnect; stops working. Reconnect;
works, etc. until eventually it starts working continuously.

This cannot be capacitive loading - there's already a significant
capacitance between RT/CT and ground.

The fact that the coupling has to be DC made me think that some small
current was flowing to ground through the scope, so I bridged C4 with a
100K resistor. It didn't make any difference.

I tried changing the IC (a pain, given that it's surface mounted), but
again it made no difference.

Any other ideas about what might be happening here.

Sylvia.

Just possibly the SCR is staying on, shorts the inverter, which
thermal limits, and recovers later? It's awfully complex.

I don't see any sign of that - the voltage across the coil is zero at
this point, whereas the capacitor C1 has about 25V across it, dropping
to zero each time the circuit is triggered, and then climbing back toe
25V. The scope shows a few steps, as it gets pumped to there, but it
doesn't continue upwards.

Back when it wasn't so lethal to ride motorcycles on the street (and I
wasn't too bright) I use to make my own CD ignitions.

I liked this topology

https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/CDI.jpg

because it was easy to drive the SCR gate with a simple RC circuit
from the points. A low value resistor from gate to ground ensures
turnoff. You could elect to kill the boost converter during the gate
pulse, too.

To get a fat spark, you need a pretty wide SCR gate pulse, to let the
whole mess ring a few cycles. I usually ran around 80 to 100 mJ per
spark, which will fire a plug no matter how fouled. Barely needs
gasoline.

Looks like I'm using a bit under 50mJ, which seems to be working, albeit
with a plug in reasonable condition.

Actually, my HV supplies were open-loop 2-transistor DC/DC converters
with full bridge rectifiers. It sort of relaxed for a while after
being shorted, then started oscillating again, which was nice.

My application is the engine of a generator. It doesn't have points, but
has some magnet/coil arrangement that produces a pulse at the correct
point in the cycle.

Certainly charging through the coil simplifies things, but I had/have no
idea what the inductance of the coil might be. Indeed, it turned out
that my coil had insulation failure in the HT side, and I had to source
a new one, so even if I'd tried to measure the old one, the new one
could have been different.

Finally got the engine running today, using this ignition circuit, and
LPG, after many hours spent cursing a PIC32MX that I was temporarily
using to generate the trigger pulse - got caught out by yet another PIC
errata - input capture doesn't work when the processor is in the idle state.

Sylvia.

 

[Cursitor Doom]

On Sat, 25 Mar 2017 20:24:16 -0400, krw wrote:

That's *exactly* the point, moron. If the other person is lying, there
is no intention of having a conversation. It's the favorite tool of you
lefties.

No, the favourite tool of the Lefties is to scream 'racist!' at you
whenever you get the better of them in an argument (which inevitably is
every time).

 

[John Robertson]

On 2017/03/25 11:12 PM, Michael A. Terrell wrote:

rickman wrote:
On 3/25/2017 3:32 AM, Michael A. Terrell wrote:
Kevin Aylward wrote:
wrote in message news:mnq8dcpnbekopn07j0cu3crq12hq0905l1@4ax.com...

On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

That's impossible, which is the whole "reasonable" thing.

Nothing whatsoever impossible about it!

Not at all. There is always doubt. It may be an unreasonable doubt
but there is _always_ doubt (what if the Earth was really flat?).
Hence, "beyond reasonable doubt".


What do you think of this sorry piece of work?

http://www.wftv.com/news/local/ayala-to-explain-why-she-wont-seek-death-penalty-against-murder-suspect-markeith-loyd/503151996





She should *immediately* be removed from office for violating her oath
of office to follow the constitution and laws of the state of Florida.
That decision isn't hers to make.

Ho hummm..

Like, what specific law says that anybody has to demand the death of
someone else? Dah....


It's her job tpoo follow the laws, not decide which ones she likes.
In that case, he murdered a police officer in front of a lot of people,
and he has a long history of violence, If she can't or won't do her job,
she needs to be fired.

What law did she violate?


What laws do you obey?

You didn't answer the question. Which was - What law did she disobey by
refusing to ask for the death penalty?

She is a Florida state attorney and can recommend that the death
sentence to be chosen by the jury. Or not. She simply expressed her
decision to not ask for the death penalty as she had come to the
conclusion, after much study, that it served no useful purpose.

Here is the Florida statute:

- 921.141 Sentence of death or life imprisonment for capital felonies;
further proceedings to determine sentence.—

http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0900-0999/0921/Sections/0921.141.html

John

 

[Cursitor Doom]

On Sat, 25 Mar 2017 23:38:20 +0000, Kevin Aylward wrote:

"Cursitor Doom" wrote in message newsb6gtd$rl8$1@dont-email.me...

On Sat, 25 Mar 2017 18:05:27 +0000, Kevin Aylward wrote:

I may not always agree with Bill, but I have never seen any evidence
that Bill lies.

boggle

https://www.youtube.com/watch?v=NX45hc0aZt0

Very good; classic. But it's because of people like Bill Sloman with
their dumbing down agenda that shows like this with their rich and
complex use of language will never be made again.