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Add an offset to AC signal

  • Thread starter Alessandro Esposito
  • Start date
A

Alessandro Esposito

Jan 1, 1970
0
I have a signal generator I use in the MHz region. It gives 2Vpp max so gr
from -1V to +1V but I need it working from 0 to 2V.... any suggestion for an
offsetting ciruit?
Thanks
 
P

Paul Burridge

Jan 1, 1970
0
I have a signal generator I use in the MHz region. It gives 2Vpp max so gr
from -1V to +1V but I need it working from 0 to 2V.... any suggestion for an
offsetting ciruit?

Er, never heard of a voltage divider?
 
F

Frank Bemelman

Jan 1, 1970
0
Paul Burridge said:
Er, never heard of a voltage divider?

Here's a divider. Where does the 2Vpp signal go, and where comes the 0-2V
signal
out?
 
A

Active8

Jan 1, 1970
0
Here's a divider. Where does the 2Vpp signal go, and where comes the 0-2V
signal
out?

|
.-.
| |
| |
'-'
|
|| |
---||------+---
|| |
|
.-.
| |
| |
'-'
|
created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

i leave the rest as an excersize 4 u. add RF chokes where needed. need
matched impedance? use a transistor or op-amp and all the stuff to go
with it.

brs,
mike
 
B

Bill Sloman

Jan 1, 1970
0
Alessandro Esposito said:
I have a signal generator I use in the MHz region. It gives 2Vpp max so gr
from -1V to +1V but I need it working from 0 to 2V.... any suggestion for an
offsetting ciruit?

Fast (video) inverting amplifier, maybe a 1.23V band-gap reference,
and a couple of resistors.

Use a divider on the reference source to set +0.5V at the
non-inverting input
to the amplifier, and use a pair of equal resistors at the inverting
input to generate an inverting gain of one.

If you are working in the MHz region, you may want a source terminated
signal to drive a 50R cable or a 50R terminated input, in which case
you might need to generate a 0V to 4V swing at the output of the op
amp (before the 50R resistor that acts as the source termination. You
then need an inverting gain of two, and 0.67V at the non-inverting
input.

In this case you can also use a non-inverting configuration, again
with a gain of two, with free end of the divider returned to -2V (for
which you could use a 2.0V reference, which you can buy of the shelf).
 
F

Frank Bemelman

Jan 1, 1970
0
Active8 said:
|
.-.
| |
| |
'-'
|
|| |
---||------+---
|| |
|
.-.
| |
| |
'-'
|
created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

i leave the rest as an excersize 4 u. add RF chokes where needed. need
matched impedance? use a transistor or op-amp and all the stuff to go
with it.

Aargh, the magic cap ;) I was thinking voltage shifters, opamps,
signals close to 0 Hz.
 
A

Active8

Jan 1, 1970
0
or passive impedance matching nets.
Aargh, the magic cap ;)

uh, "magic cap"? that's what witches supposedly made a paste out of.
they supposedly rubbed it on a broom-stick and straddled it (naked) with
their vulva right on the "magic spot".

brs,
mike
 
A

Alessandro Esposito

Jan 1, 1970
0
yep I will work with 50Ohm impedence... thanks for the suggestions
Ale
 
B

Bill Sloman

Jan 1, 1970
0
Active8 said:
or passive impedance matching nets.


uh, "magic cap"? that's what witches supposedly made a paste out of.
they supposedly rubbed it on a broom-stick and straddled it (naked) with
their vulva right on the "magic spot".

You've been reading too much imaginative fiction, otherwise known as soft porn.
 
A

Active8

Jan 1, 1970
0
On 15 Oct 2003 02:11:11 -0700, Bill Sloman, said...
You've been reading too much imaginative fiction, otherwise known as soft porn.
you assume too much along those lines and therefor are probably the one
with the problem.

it had nothing to do with porn. it was something that popped up in a
search. i was looking for info on nerve agent antidotes like we had in
the army. atropine is given in nerve agent antidotes to seize up the
agent which is cleaned out with a follow up shot of PAM II Cl. atropine
is also present in belladonna mushrooms and doctors sometimes screw up
and administer more atropine which will poison you.

brs,
mike
 
B

Bill Sloman

Jan 1, 1970
0
Active8 said:
On 15 Oct 2003 02:11:11 -0700, Bill Sloman, said...
you assume too much along those lines and therefor are probably the one
with the problem.

it had nothing to do with porn. it was something that popped up in a
search. i was looking for info on nerve agent antidotes like we had in
the army. atropine is given in nerve agent antidotes to seize up the
agent which is cleaned out with a follow up shot of PAM II Cl. atropine
is also present in belladonna mushrooms and doctors sometimes screw up
and administer more atropine which will poison you.

All of which makes sense, but has little connection with with
fantasies about what witches might have smeared on their broomsticks,
and why.

Medical practitioners of the early enlightenment - 17th century,
roughly - from time to time wrote down what they put into their pills,
potions and salves and sometimes also wrote down what they thought
each ingredient did, so we have some idea of what they used, and why
they thought each one was useful.

Witch persecution fell out of favour at around that time, largely
because it was realised that persecuting witches was effectively
nothing more than a profitable business for the persecutors, who had
worked out a technique for framing elderly women as witches which
produced an adequately convincing public spectacle.

The documents about the practice of witchcraft, which were tortured
out of the victims of this perculiarly unpleasant confidence trick,
give some insight into the prejudices of the persecutors, but are not
otherwise to be relied on.
 
A

Active8

Jan 1, 1970
0
On 16 Oct 2003 02:20:40 -0700, Bill Sloman, said...
All of which makes sense, but has little connection with with
fantasies about what witches might have smeared on their broomsticks,
and why.

i brought up witches and belladonna in response to "magic cap".

i brought up the above to clarify where i got the info. ever do a
search? lots of interesting synopses/descriptions turn up, some of which
i just can't help but read, especially when it comes down to the kind of
stuff you don't learn in history class.
Medical practitioners of the early enlightenment - 17th century,
roughly - from time to time wrote down what they put into their pills,
potions and salves and sometimes also wrote down what they thought
each ingredient did, so we have some idea of what they used, and why
they thought each one was useful.

Witch persecution fell out of favour at around that time, largely
because it was realised that persecuting witches was effectively
nothing more than a profitable business for the persecutors, who had
worked out a technique for framing elderly women as witches which
produced an adequately convincing public spectacle.

not much different from the man created concept of pergatory, which was
used to sell indulgences.
The documents about the practice of witchcraft, which were tortured
out of the victims of this perculiarly unpleasant confidence trick,
give some insight into the prejudices of the persecutors, but are not
otherwise to be relied on.
there are other things in recorded history that may be unreliable, also.
some of it's believable enough. if i were a witch... it's like johnny
dare from the eagle (?) radio station in KCMO said in response to
someone talking about a man's feminine side. he said, "If I had a
feminine side, I'd be sticking my fingers in it."

i can bvelieve this belladonna thing, though. read Carlos Casteneda's
series on Don Juan, the Yaqui Indian sorcerer. psychotropic plants
*were* part of the picture. as for Wiccans, damned if i know what all
they do.

anyway... IMHO, those who persecute others rarely know jack about those
they persecute, are sometimes not much better humans, and therefore are
the more vile of the two.

brs,
mike
 
F

Fred Bloggs

Jan 1, 1970
0
Alessandro said:
I have a signal generator I use in the MHz region. It gives 2Vpp max so gr
from -1V to +1V but I need it working from 0 to 2V.... any suggestion for an
offsetting ciruit?
Thanks

Please view in a fixed-width font such as Courier.


C
Vs o---||------+----> Vs,ac + Voffset
|
/
50R
/
\
|
|
Voffset




|
|
1 0dB +- - - -------
Vout,ac= ------- | /
1 | /
1 + ---- | / |
jwRC |
-+-------+---------------
1
 
F

Fred Bloggs

Jan 1, 1970
0
Fred said:
Please view in a fixed-width font such as Courier.


C
Vs o---||------+----> Vs,ac + Voffset
|
/
50R
/
\
|
|
Voffset




|
|
1 0dB +- - - -------
Vout,ac= ------- | /
1 | /
1 + ---- | / |
jwRC |
-+-------+---------------
1

oR-
Please view in a fixed-width font such as
Courier.



C
Vs o---||-----+-------> TO 50 OHM LOAD
|
)
RFC
)
)
|
|
Voffset
 
R

Robert Monsen

Jan 1, 1970
0
[trim]
Witch persecution fell out of favour at around that time, largely
because it was realised that persecuting witches was effectively
nothing more than a profitable business for the persecutors, who had
worked out a technique for framing elderly women as witches which
produced an adequately convincing public spectacle.

The documents about the practice of witchcraft, which were tortured
out of the victims of this perculiarly unpleasant confidence trick,
give some insight into the prejudices of the persecutors, but are not
otherwise to be relied on.

I've heard theories that witchcraft was associated with ergot contamination
of rye flour. Eating ergot over a period of time can produce halluinogenic
effects, which leads to all manner of odd reports (LSD is made from ergot).
The places where ergot contamination historically occured maps pretty
closely to those places where witch trials took place. The practice stopped
when better methods of protecting against ergot poisoning were found.

Regards,
Bob Monsen
 
A

Active8

Jan 1, 1970
0
On Thu, 16 Oct 2003 22:38:28 GMT, Robert Monsen, said...
I've heard theories that witchcraft was associated with ergot contamination
of rye flour. Eating ergot over a period of time can produce halluinogenic
effects, which leads to all manner of odd reports (LSD is made from ergot).
The places where ergot contamination historically occured maps pretty
closely to those places where witch trials took place. The practice stopped
when better methods of protecting against ergot poisoning were found.

Regards,
Bob Monsen
you know, i've also heard that, IIRC. and i saw a movie once, too. i
can't remember the name. it may not have been about ergot. no, it was
about an old house with a legend of witchcraft. crazy old ladies that
baked bread. the home owners found some kind of fugus and the husband
got some researchers together after he injected himself with it. it gave
them "super-human" abilities and really screwed them up.

but i remember that ergot angle now.

brs,
mike
 
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