Op amps problem Gain Calculation

[Frank]

"Frank" <Francis.invalid@hotmail.com> wrote in message
news:438bd5a3$1@news.starhub.net.sg...

I am injecting the DAC output from TI DAC290x-EVM to ADC (Analog AD9218).
When I connect I channel from DAC to I & Q channel of ADC, I am seeing
vastly
different digital outputs on ADC (sampling three pins on oscilloscope).
What
might
be the cause?

When using logic analyzer to sample ADC outputs, i am getting strange
outputs.

Right channel,
bit 9,8,7,6 stick to 1, bit 0 stick to zero, while bits 5,4,3,2,1 varies
during active, while sticking to
1 during idle mode.

Left channel,
bit 7,5 stick to 0, bit 9,4 switches during active, stick to 1 in idle mode,
bit 8,6,3,2 switches during
active, stick to 0 during idle (I expect 9:2 of both channel to behave in
this manner), bit 1:0 are
switching during idle and active (noise during idle mode).

I double checked my settings, but found nothing wrong. How can I proceed
now?

 

[Meindert Sprang]

"Frank" <Francis.invalid@hotmail.com> wrote in message
news:438d4a78$1@news.starhub.net.sg...

When using logic analyzer to sample ADC outputs, i am getting strange
outputs.

Right channel,
bit 9,8,7,6 stick to 1, bit 0 stick to zero, while bits 5,4,3,2,1 varies
during active, while sticking to
1 during idle mode.

Left channel,
bit 7,5 stick to 0, bit 9,4 switches during active, stick to 1 in idle
mode,
bit 8,6,3,2 switches during
active, stick to 0 during idle (I expect 9:2 of both channel to behave in
this manner), bit 1:0 are
switching during idle and active (noise during idle mode).

Do you use any bus control signal (RD in combination with CE for the ADC for
example) to trigger the logic analyser? If not, you are just measuring all
bus activity, not just the output from the ADC.

Meindert

 

[Pippa Reeves]

On Fri, 02 Dec 2005 12:27:10 +0800, Frank wrote:

ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

I don't know what you people are talking about.
Back to my question, how do I make a +-5V?

+ - 5volts is actually 2 supplies, each giving out 5 volts, but one supply
has it's negative output connected to the 0 volt (common), the other
supply has its positive output connected to the 0 volt (common).

The effect is if you measure from the 0 volt (common) to one supply rail,
you will measure positive 5 volts, measuring from the 0 volt to the other
5 volt supply rail will be negative 5 volts.

Your original assumption that if you measured from the +5 rail
to the -5 rail you would find 10 volts is correct, but don't forget that
BOTH of the 5 volt supplies need to reference to the 0 volt as the current
drawn in the -5 circuitry may not balance the current drawn by the +5 volt
circuits..... without a 0 volt reference, you could end up with +3 volts
and -7 being supplied (the ratio between the + and - would depend on the
current being drawn from each of the 2 supplies)


Now, as for the +3 volt and +3.3 volts you also mentioned in your original
post, these would also have their negative rail tied to the 0 volt (common).

This is the 'normal' way that these type of multi voltage computer power
supplies are hooked up.

So your supply would have 5 output connections....
1, 0 volts (common to all 4 of the supplies!)
2, +5 volts
3, -5 volts
4, +3 volts
5, +3.3 volts

Pip

 

[Jerry Avins]

Fred Marshall wrote:

"Frank" <Francis.invalid@hotmail.com> wrote in message
news:438fa5a4@news.starhub.net.sg...

I have a large board which asks for three power supplies, +3V, +3.3V and
+-5V.
First two can be easily satisfied with two HP power supplies (each has its
own
GND pin also). Regarding +-5V, can I replace with an HP power supply set
to
10V, -5V pin connect to HP's ground and +5V to power?


You might with some caveats.
First, the intended +-5v supply needs to be floating with respect to the
other supplies.
Then the 10v voltage difference can be reference wherever you want in theory
and often in practice.

The challenge is: now that you've floated the supply, how will you reference
it to the ground or 0v point on the board?

Think of the +-5v supply as a 10v battery. A battery "floats" with no
problem.
Unless you do more, the result looks like this:


+------------------------------>+5v
|
|
+----+ +--------------->+3.3v
| 10v| +----+
+----+ |3.3v| +----------+3v
| +-+--++----+
| | |3.3v|
| | +-+--+
| | |
| | |
| +-----+---------> 0v: the reference for +3.3v, +3v
|
|
|
+------------------------------>-5v

With the 10v battery floating, there is no reference to the
other batteries. Current flowing through the circuit board will cause
the +/-5v terminals to go almost anywhere relative to 0v. Depending on
what's on the board,
the +5v terminal could end up at -6v and the =5v terminal at -15v (both
relative to 0v of course).



+------+----------------------->+5v
| |
| | +--------------->+3.3v
+----+ | +----+
| 10v| | |3.3v| +----------+3v
+----+ ++-+ +-+--++----+
| |R1| | |3.3v|
| ++-+ | +-+--+
| | | |
| | | |
| +-------+-----+---------> 0v: the reference for +3.3v, +3v
| +--+
| |R1|
| ++-+
| |
+------+----------------------->-5v

A resistor divider with current much higher than the +/-5v
loads and connected to the 0v reference will refer the +/-5v
to the rest of the batteries.
It's not a very elegant or even practical solution but it makes the
point to address your question.

You can make Fred's solution more practical by adding an operational
amplifier that can deliver the difference between +5 and -5 currents.

+------+-------------------------------------------->+5v
| |
| | +--------------->+3.3v
+----+ | +----+
| 10v| | |3.3v| +---------+3v
+----+ ++-+ +-+--+ +----+
| |R1| +----------+ | |3.0v|
| ++-+ | |\ | | +-+--+
| | +---|-\ | | |
| | | +---+----------+------+---------> 0v
| +--------|+/
| +--+ |/
| |R1|
| ++-+
| |
+------+----------------------->-5v

Is it worth it?

Jerry
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

 

[c d saunter]

Frank (Francis.invalid@hotmail.com) wrote:

....

: I don't know what you people are talking about.
: Back to my question, how do I make a +-5V?

'Buy one' is the most sensible suggestion I've seen elsewhere on the
thread.

*BEWARE*
Another one I've seen mentioned is to get 2 stock 5V supplies, A and B,
and connect the +5V of A to the 0V of B, and call pair this 0V, thus
making the 0V of A -5V and the 5V of B +5V.
*BEWARE*

This may or may not work - many lab power supplies and some bricks
conenct the 0V from the DC side to the mains earth, so doing this
with two such supplies will cause funny noises, bad smells and possibly
worse as the magic smoke escapes.

If you're not sure, don't try ths aproach!

---

cds

 

[Frank]

"Frank" <Frank@Frank.com> wrote in message
news:dmk525$34f$1@reader01.singnet.com.sg...

"Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote in message
news:11oqpeup6ur1k50@corp.supernews.com...
"Frank" <Francis.invalid@hotmail.com> wrote in message
news:438d4f5d$1@news.starhub.net.sg...
In my digital side, I have a PHY_EN pin which is high when the digital
circuit repetitively sends
out same data, and the digital circuits work for 30us and idle for
10us.
On
logic analyzer, I set
the LA to start filling in the internal memory (256K) once PHY_EN is
high,
thus I can capture
20 repetitions. I am sure the data capture is correct.

And I am not. this PHY_EN signal, what does it drive on the processor?
I can imagine that it just signals the processor data is available and
that
consequently, the processor issues bus cycles (set an address or CE,
activate RD, read data, deactivate Rd and CE) to read the data. This
means
that data on the bus during this 30us is not data from the ADC all the
time.
Only when the ADC is read during the bus read cycle, valid ADC data is
readable on the bus.

Meindert



Ah! I understand what you mean now. PHY_EN is a stable signal, while my
clock
period is 25ns, in each frame, digital side is sending some 1200 I/Q
samples,
one pair of samples each cycle and unchanged throughout the clock cycle.

From the datasheet of ADC, I don't see there is any Rd or CD signal, it's
as
plain as ADC outputs are hold stable and change every 25ns.

After all is done, I think I had better flag a "faulty ADC board" message
to
the up layer. since even when I disconnect ADC input, many of the pins
mentioned
below still to high level, sampled by a logic analyzer's 400MHz clock.

Left channel,
bit 7,5 stick to 0, bit 9,4 switches during active, stick to 1 in idle
mode,
bit 8,6,3,2 switches during
active, stick to 0 during idle (I expect 9:2 of both channel to behave in
this manner), bit 1:0 are
switching during idle and active (noise during idle mode).

Sigh! What should I say!!! After working a number of times, I realized that
the
god damned LA strobes are broken, and managed to sort out the broken ones
with an everchanging pin. With this discovery, I think I will get on much
easier.

 

[diehard67]

try somthing like this the atached picture

i used a transister to swich the 9 volt rail directly to the led, the 555
timer can't putout enough power to run all those leds but it can swich a
tranister to cut it a larger power sorce, you may also try redusing the
resister value


--
diehard67
http://www.geocities.com/diehard67
"Frank" <mayo9747@bellsouth.net> wrote in message
news:aG8nf.51335$i7.12217@bignews2.bellsouth.net...

Here is a copy of the schematic of my not so bright IR LED's

 

[John Fields]

On Fri, 16 Dec 2005 21:21:52 GMT, "diehard67" <ax@bx.cx> wrote:

try somthing like this the atached picture

i used a transister to swich the 9 volt rail directly to the led, the 555
timer can't putout enough power to run all those leds but it can swich a
tranister to cut it a larger power sorce, you may also try redusing the
resister value

---
Sometimes the price of the read isn't worth the reward.

--
John Fields
Professional Circuit Designer

 

[default]

On Fri, 16 Dec 2005 21:25:27 GMT, "diehard67" <ax@bx.cx> wrote:

try somthing like this the atached picture

i used a transister to swich the 9 volt rail directly to the led, the 555
timer can't putout enough power to run all those leds but it can swich a
tranister to cut it a larger power sorce, you may also try redusing the
resister value

Read the data sheet on the 555. You are showing a pair of 34 ohm
resistors as timing elements? PIn 7 (discharge) has an open
collector, when it switches to ground, it is pulling a lot of current
from the battery through one 34 ohm resistor to ground and more than
is healthy for the discharge transistor. Wasting valuable battery
power there.

Increase the resistance's and decrease the cap. There's a nomograph
for the astable circuit in the book so you can adjust the frequency
easily.

Your efficiency would be better with the LED(s) in the collector leg
and there would need to be a limiting resistor on the base of the
driver transistor.

Look at some representative circuits on the web.
--

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[LRCR]

Hi Jasen

Attached is you suggested circuit redrawn in Workbench. When I looked
at it, I like the idea how D1 and D2 are used to terminate through the
voltage divider powered by -5v and +5v (R1||R2= 75ohms) and then
reverse D1 and D2 to no termination. Very clever. I ran this circuit
on the simulator and toggle J1 between 5v and 0v. Unfortunately, I
saw no change on the right side of R11. Checking on the circuit I
notice that Q5 and Q1 can never turn on regardless if the right side
of R8 is 0v or 5v. The BE (Base- emitter) of Q1 never completely gets
forward bais to turn the transistor. The same is Q5. I can't seem to
see any bipolar configuration for Q2 to switch Q5 and Q1 on or off.
Can you see if I redrew your schematic correct. I hope to get your
schematic to work on Workbench first before I try to bread-board it.
Your idea for the diode to switch on or off the termination make
sense. I just have to get the logic controls to work proper. Please
send me your feedback.

Caesar

 

[Jasen Betts]

On 2006-02-04, LRCR <xyz@ix.netcom.com> wrote:

Hi Jasen

Attached is you suggested circuit redrawn in Workbench.

It fell off on the way here. I don't have workbench here.

When I looked at it, I like the idea how D1 and D2 are used to terminate
through the voltage divider powered by -5v and +5v (R1||R2= 75ohms) and
then reverse D1 and D2 to no termination. Very clever.

Not my invention, I copied that idea from the RF switch of a games
console.

I ran this circuit on the simulator and toggle J1 between 5v and 0v.
Unfortunately, I saw no change on the right side of R11. Checking on
the circuit I notice that Q5 and Q1 can never turn on regardless if the
right side of R8 is 0v or 5v.

I've had another look at my drawing, the top and bottom transistors were the
wrong types, swap them. sorry.

--+--- +5
|
10K
source | 2N3904
| 1N914 |
| +-->|--+-------C >E-------+---- -5
| | | B |
| 150R | | |
| | | |---[33k]-'
\ | === 100pF |
\ / | 1K .---[10K]-- control
X --+-- 0V | .2N3906 | (0 or 5V)
/ \ | C ' B
/ | === 100pF ^B---[10K]--+-C >E-- 0V
| | | E | `.
| | | | | 2N33904
| | | |--[33K]-. 47K
| 150R | | | |
| | | B | |
| +--|<--+-------C <E------+--+--- +5
| 1N914 |
scope | 2N3906
10K
|
--+--- -5

TTL-swittched broadband terminator concept (rev1.1).

Bye.
Jasen

 

[LRCR]

Thanks for your input regarding the 4 bipolar/2 diode approach.

Caesar

On Sun, 19 Feb 2006 04:56:29 -0000, Jasen Betts <jasen@free.net.nz>
wrote:

On 2006-02-18, LRCR <xyz@ix.netcom.com> wrote:

I am designing a switchable 75 ohm terminator circuit for a video
application using a Enhance Mode N-Channel MOSFET, ZVN4106F (ZETEX)
and a 75 ohm resistor. Please see the JPG attachment. The Source is
connected to ground. The Drain is connected to a 75ohm resistor and
the other side of the 75ohm resistor end to the video source-to-a
video analyzer coax line. The gate of the FET is connect to a TTL
source. The video source is sweeping video from 1 to 30 MHz. When the
TTL is high, the FET turns on and the analyzer sees the termination.
The frequency response is flat all the way to 30 MHz. When the TTL is
low, the FET turns off and the analyzer sees the unterminated
video,but the frequency response rolls down to 15.4MHz at -3dB. Doing
my calculation using 15.4MHz, 75ohm load and fc=1/2pi*RC. The
capacitance of the FET I am using when it is off is about 137pF. Too
high for my application since I need to have a flat response within
0.1 dB range all the way to 20MHz. I figure if I can get a low
capacitance Drain-to-source Enhance Mode N-Channel MOSFET of about
15pF or below, I'll be OK. Any idea where I can find a FET like this?

put an inverse voltage on the gate, that'll increase the capacitance a bit.

By the way. In the past, someone sent me a 4 Bipolar/2 diode approach
to the switchable termination problem. This circuit worked great,

that was me, glad to hear it.

but with a cost. I need to use a -5v source that is not part of the
prototype design. The design will provide a +5v and a +12V voltage
source. Also, if i did provide a -5v souce, this source will need to
support 400mA load current since I would have to use 8 of these
switchable circuit(50mA each. Too high.

possibly you could run them at a lower voltage, eg +2v and -2V

The MOSFET approach on the
other hand draws very little current and can use an only +5v design
scheme. So I have to make the MOSFET approach to work, 1 to 20MHz
flatness. Any idea will be helpful.

Bye.
Jasen

 

[Daniel Joseph Min]

On 1 Mar 2006, "WQ" <wq@email.com> wrote:

hancock4@bbs.cpcn.com wrote:
Would anyone know of sources to learn more about early forms of
televsion broadcasting? For example, how many people had TV sets from
1940 onward, before the big development of commercial TV in the late
1940s? We know there were experimental stations and TV sets, but were
they literall just a handful (ie under 100?) owned by engineers, or
more than that (ie around 1000?) owned by the general public.
Considering the early TV sets were very expensive and there was very
little on, I can't see how that many people would buy them.

--- Check this out for a start:
http://www.earlytelevision.org/us_tv_sets.html

Bookmarked!

Daniel Joseph Min
http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x2B1CCFE7

*Download Min's Banned (Freeware) Books:
http://www.2hot2cool.com/11/danieljosephmin/

*Min's Google-Archived Home Page On The WWW:
http://groups.google.com/groups?selm=XJBDEJF138262.9022453704@anonymous.poster

 

[JeffM]

Can anybody explain to me exactly how this circuit functions,
Gareth Edwards

Gareth, any chance you can reduce the size of the circuit Diagram?
Daniel

http://groups.google.com/groups/search?q=a-newsgroup-that-does-not-have-binaries-in-its+-Muskie

 

[Daniel]

JeffM wrote:

Can anybody explain to me exactly how this circuit functions,
Gareth Edwards
Gareth, any chance you can reduce the size of the circuit Diagram?
Daniel

http://groups.google.com/groups/search?q=a-newsgroup-that-does-not-have-binaries-in-its+-Muskie

No, Jeff, I didn't ask to be sent to a NG that doesn't support binaries,
did I?

Daniel
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

 

[JeffM]

http://groups.google.com/groups/search?q=a-newsgroup-that-does-not-have-binaries-in-its+-Muskie
JeffM

No, Jeff, I didn't ask to be sent to a NG that doesn't support binaries,
did I?
Daniel

You are at one NOW.

You appear to have a tenuous grasp of how Usenet works.
Most groups are text-only.
The majority of servers Usenet strip off attachments.

It is an aberration that apparantly yours and Gareth's don't.
Posting attachments is discouraged
in any group whose name does not include *binary* or *binaries*
because the majority of folks will not see them.

Folks who want to post schematic graphics
should go to a group like alt.binaries.schematics.electronic.

 

[Daniel]

JeffM wrote:

http://groups.google.com/groups/search?q=a-newsgroup-that-does-not-have-binaries-in-its+-Muskie
JeffM
No, Jeff, I didn't ask to be sent to a NG that doesn't support binaries,
did I?
Daniel

You are at one NOW.

You appear to have a tenuous grasp of how Usenet works.
Most groups are text-only.
The majority of servers Usenet strip off attachments.

It is an aberration that apparantly yours and Gareth's don't.
Posting attachments is discouraged
in any group whose name does not include *binary* or *binaries*
because the majority of folks will not see them.

Folks who want to post schematic graphics
should go to a group like alt.binaries.schematics.electronic.

If that's what you meant, why didn't you say so the first time? No Worries!

It must be, as you say, that both my and Gareth's servers do support
posting of binaries. Rather that Gareth going to another NG, which I may
or may not subscribe to, and starting another thread there, my
suggestion would be to go to somewhere like:-

http://imageshack.us/

and post his circuit there, after, as I typed a while back, reducing its
size, so that I don't have to scroll around to see what's where.

Daniel

*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

 

[Tater Schuld]

"Gareth Edwards" <gareth.edwards100@btinternet.com> wrote in message
news:dva6rk$558$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com...

Hi

Can anybody explain to me exactly how this circuit functions, what it
does,
and why were the components chosen i.e. how were the resistor values
calculated etc.
Where it says "solar +ve", this is the positive pole of a small solar
panel.
The circuit works on 2 AA batteries in series.
L1, L2, R1, R2, and R3 are all resistors.
The capacitor is a 101. 100pF ceramic disc type.
Two transistors are S8050 type.
Diode is a 1N5819.

boy at first glance this circuit doesn't look like it does anything!

you got a power on led branch, that makes sense
you got an amplifier (maybe set up as an op amp?) to kick on a second
transistor that doesn't have an output.

since it is solar (i.e. solar +ve) I am assuming it is a light actuated
controller, but I don't see what it controls.

 

[Gareth Edwards]

"Tater Schuld" <Tater1337@yahoo.com> wrote in message
news:W3_Sf.40$Vd3.32@fe07.lga...

"Gareth Edwards" <gareth.edwards100@btinternet.com> wrote in message
news:dva6rk$558$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com...
Hi

Can anybody explain to me exactly how this circuit functions, what it
does,
and why were the components chosen i.e. how were the resistor values
calculated etc.
Where it says "solar +ve", this is the positive pole of a small solar
panel.
The circuit works on 2 AA batteries in series.
L1, L2, R1, R2, and R3 are all resistors.
The capacitor is a 101. 100pF ceramic disc type.
Two transistors are S8050 type.
Diode is a 1N5819.

boy at first glance this circuit doesn't look like it does anything!

you got a power on led branch, that makes sense
you got an amplifier (maybe set up as an op amp?) to kick on a second
transistor that doesn't have an output.

since it is solar (i.e. solar +ve) I am assuming it is a light actuated
controller, but I don't see what it controls.

Apologies for posting the diagram first of all.
The circuit is out of a solar powered lantern for the garden. It is
*supposed* to charge the battery during daylight hours, and then the light
(l.e.d.) comes on in the night.
I am not 100% sure that L1 and L2 are resistors, maybe they are inductors?
that would explain why they are labelled as they are. I am no electronics
genius but they look exactly like the other resistors in the circuit except
that they are slightly larger and they are green.
I would like to know how the circuit works and why each component was
chosen, because I want to use the circuit for something else.

Cheers

 

On Dec 10, 3:54 pm, Kris Peeters <$fname.$ln...@skynet.be.invalid>
wrote:

avaruusm...@suomi24.fi wrote:
What kind of possibilities there are to send on/off information
from switch button to computer? Is there simple components or
equipments, which can told there state to computer by
bluetooth, WLAN, RDIF or other ways?Try Google for *X10* or check
http://en.wikipedia.org/wiki/X10_(industry_standard)

--
Kris.

X10 seems to be suitable for most cases I have in my mind, but they
migth not work with Linux.

The other use of remote control with PC could be to start programs
remotely. What would be best way to do this?
Is there RF receiver cards, which can separate many transmitters,
available to PC?