Maker Pro
Maker Pro

Low volt noise gen

L

Larry Redmore

Jan 1, 1970
0
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Larry R.
 
A

Andrew Holme

Jan 1, 1970
0
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Larry R.

What noise bandwidth do you require?

How about a super-regenerative receiver with no input signal?
 
C

Chuck

Jan 1, 1970
0
Larry said:
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Larry R.

Look here:

http://www.ciphersbyritter.com/RADELECT/MEASNOIS/NOISMEA1.HTM
Junction Noise Measurements I

Chuck
 
R

rebel

Jan 1, 1970
0
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Why not use a switchmode step-up and generate the higher voltage from your "down
to 4 volts" source? Of course, you'll have to filter the output carefully to
avoid a noise contibution.
 
J

John Devereux

Jan 1, 1970
0
Larry Redmore said:
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Depending on your definition of "truly random", you could use a
cascade of ac-coupled opamp stages to amplify the noise from a high
value resistor (e.g. 10M).
 
J

John Larkin

Jan 1, 1970
0
Depending on your definition of "truly random", you could use a
cascade of ac-coupled opamp stages to amplify the noise from a high
value resistor (e.g. 10M).

And there are some truly terrible opamps around, with noise density
scores of times higher than a resistor.

What's that National dip8 audio power amp, the one in the Radio Shack
amp/speaker boxes? That hisses like gangbusters.

John
 
S

Spehro Pefhany

Jan 1, 1970
0
And there are some truly terrible opamps around, with noise density
scores of times higher than a resistor.

What's that National dip8 audio power amp, the one in the Radio Shack
amp/speaker boxes? That hisses like gangbusters.

John

LM386?


Best regards,
Spehro Pefhany
 
W

Wim Ton

Jan 1, 1970
0
Larry Redmore said:
I am looking for a circuit that will generate random noise and run on
a supply as low as 4 volts. Typically, this cannot be done with diode
or transistor junction noise. The minimum potential seems to be around
9V. To overcome this, simulated noise is sometimes generated with
digital IC's, but this is not truly random.

Does anyone know of a circuit that will generate genuine random noise
and operate down to 4 volts, without specialized components?

Larry R.

I have seen some designs using a CMOS invertor chain:

1. A chain with a variable length. The length is controlled by some LFSR
outputs and the read strobe
The input of the LFSR is the output of the invertor chain, latched by a
crystal clock.
The random is an output of the LFSR.

2. Phase noise of a CMOS invertor chain

Wim
 
P

Phil Allison

Jan 1, 1970
0
"Spehro Pefhany"


** No way - the LM386 is very quiet.

From myself on SED Jan 22 this year:

" Natsemi do not supply a noise spec for their LM386 audio amp.

I used the most basic circuit with a gain of * 26 dB * and fitted a 47uF
bypass cap on pin7.

Input pins 2 & 3 were grounded to pin 4, DC supply came from a 9 volt radio
battery.
The output signal on pin 5 was fed first to a 60dB gain mic pre-amp and then
a 22Hz to 20 kHz audio band filter with 12 dB/ oct roll-off slopes.


The noise signal was observed on a scope and found to be hum free, then
measured with a True RMS voltmeter with over 100kHz bandwidth. The reading
was 144mV rms.


So, the LM386's output noise level was 144 uV rms.


Relative to a 3 volt rms output level, the s/n ratio is around 87 dB.

Fine for the intended applications. "



........ Phil
 
J

John Larkin

Jan 1, 1970
0
"Spehro Pefhany"



** No way - the LM386 is very quiet.

Yeah, the RatShack amp uses a 386. That must have used a custom noisy
version.

John
 
P

Phil Allison

Jan 1, 1970
0
"John Larkin"
"Phil Allison"

** Explanation snipped out of sight by Mr Ego Larkin ....

Yeah, the RatShack amp uses a 386. That must have used a custom noisy
version.

John


** When you have nothing sane to say John

- learn to shut the **** up.

Should keep you quiet for a while.





....... Phil
 
M

Michael A. Terrell

Jan 1, 1970
0
Phil said:
"John Larkin"
"Phil Allison"

** Explanation snipped out of sight by Mr Ego Larkin ....


** When you have nothing sane to say John

- learn to shut the **** up.

Should keep you quiet for a while.

...... Phil


Take your own advice, Phillis.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
J

John Popelish

Jan 1, 1970
0
Phil said:
** No way - the LM386 is very quiet.

From myself on SED Jan 22 this year:

" Natsemi do not supply a noise spec for their LM386 audio amp.

I used the most basic circuit with a gain of * 26 dB * and fitted a 47uF
bypass cap on pin7.

Input pins 2 & 3 were grounded to pin 4, DC supply came from a 9 volt radio
battery.
The output signal on pin 5 was fed first to a 60dB gain mic pre-amp and then
a 22Hz to 20 kHz audio band filter with 12 dB/ oct roll-off slopes.


The noise signal was observed on a scope and found to be hum free, then
measured with a True RMS voltmeter with over 100kHz bandwidth. The reading
was 144mV rms.


So, the LM386's output noise level was 144 uV rms.


Relative to a 3 volt rms output level, the s/n ratio is around 87 dB.

Fine for the intended applications. "

Thanks for an actual data point,
instead of an unsupported opinion.
 
K

krw

Jan 1, 1970
0
"John Larkin"
"Phil Allison"


** Explanation snipped out of sight by Mr Ego Larkin ....




** When you have nothing sane to say John

- learn to shut the **** up.

Should keep you quiet for a while.

Wow!

In this corner we have a nice black pot. What do I have for an
opening bid?
 
J

John Larkin

Jan 1, 1970
0
Thanks for an actual data point,
instead of an unsupported opinion.

My opinion isn't unsupported. I have two of these boxes, and they both
hiss.

John
 
J

John Popelish

Jan 1, 1970
0
John said:
My opinion isn't unsupported. I have two of these boxes, and they both
hiss.

Is the hiss originating from the LM386 chips or from some
other component? Phil's data shows the result of a test of
the LM386 generated noise.
 
J

John Larkin

Jan 1, 1970
0
Is the hiss originating from the LM386 chips or from some
other component? Phil's data shows the result of a test of
the LM386 generated noise.

144 uV RMS is a pretty good amount of apparently-wideband noise,
actually.

John
 
P

Phil Allison

Jan 1, 1970
0
"John Larkin"
John Popelish


** It's totally unsupported by objective data.

Or any sane thought.


144 uV RMS is a pretty good amount of apparently-wideband noise,
actually.



** When you have nothing sane to say John

- learn to shut the **** up.

Should keep you quiet for a long while.





........ Phil
 
J

John Larkin

Jan 1, 1970
0
"John Larkin"
John Popelish



** It's totally unsupported by objective data.

Or any sane thought.






** When you have nothing sane to say John

- learn to shut the **** up.

Should keep you quiet for a long while.

I work in picoseconds mostly, so time's up.

John
 
Top