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Sine wave generator

Hi,

I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?

Thanks a lot

Joseph Zammit
Malta
 
J

John Woodgate

Jan 1, 1970
0
dated said:
I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?

You can do it with one op-amp that has a gain well over 3 at 100 kHz.
Google for 'Wien Bridge'. The problem is not getting it to oscillate but
controlling the amplitude so you don't get a clipped sine wave. There
are many ways of doing it; the best, but costly, is a vacuum thermistor
bead. You can use a FET as a voltage-controlled resistor.

It won't do 0 to 100 kHz in one range, though. If you want that (I can't
think why), Google for 'Exar function generator'. but it's not as much
fun as the Wien bridge solution.
 
J

Joel Kolstad

Jan 1, 1970
0
I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?

If you want an "almost all digital" solution, Analog Devices has
microcontrollers with built-in DDS generators that will easily meet your
specifications. (See:
http://www.analog.com/en/press/0,2890,3%5F%5F96529,00.html) This is
probably serious overkill, however, and certainly not the cheapest solution
and nowhere close to the lowest power. The main benefit over, e.g., a wien
bridge is that you simply program the output frequency with a digital word,
and the result is as accurate as your (e.g., crystal) clock source (if
accuracy was unspecified, a crystal is generally considered "far more than
accurate enough, with no calibration or drift to worry about...").
 
L

Leon

Jan 1, 1970
0
Joel said:
If you want an "almost all digital" solution, Analog Devices has
microcontrollers with built-in DDS generators that will easily meet your
specifications. (See:
http://www.analog.com/en/press/0,2890,3%5F%5F96529,00.html) This is
probably serious overkill, however, and certainly not the cheapest solution
and nowhere close to the lowest power. The main benefit over, e.g., a wien
bridge is that you simply program the output frequency with a digital word,
and the result is as accurate as your (e.g., crystal) clock source (if
accuracy was unspecified, a crystal is generally considered "far more than
accurate enough, with no calibration or drift to worry about...").

A software DDS running on a suitable MCU and DAC should be suitable. An
AT90S2313 clocked at 10 MHz should be able to manage 100 kHz.

Leon
 
P

Phil Allison

Jan 1, 1970
0
** Groper alert !!

I need to design a simple variabel sine wave generator up 100kHz.


** Variable by what means ?

A knob?

A control voltage.

A light beam ?

ESP ???


Does anyone know of single chip solution?


** Tell us what is the actual problem first.

Or be condemned to hell for eternity as another TROLL.>





........ Phil
 
T

Tim Wescott

Jan 1, 1970
0
John said:
You can do it with one op-amp that has a gain well over 3 at 100 kHz.
Google for 'Wien Bridge'. The problem is not getting it to oscillate but
controlling the amplitude so you don't get a clipped sine wave. There
are many ways of doing it; the best, but costly, is a vacuum thermistor
bead. You can use a FET as a voltage-controlled resistor.

It won't do 0 to 100 kHz in one range, though. If you want that (I can't
think why), Google for 'Exar function generator'. but it's not as much
fun as the Wien bridge solution.

Search around for the tiniest incandescent lamp you can find -- if you
can find a 6V grain-of-wheat bulb you can use that for the resistive
element. I suspect a small thermistor stuck in foam would work almost
as well as the vacuum thermistor, and possibly better than the lamp.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
B

BobG

Jan 1, 1970
0
I need to design a simple variabel sine wave generator up 100kHz.
=====================================
I recall Mr Hewlitt and Mr Packard made a Very Able sine wave
oscillator back in the day... in Palo Alto as I recall....
 
R

Rene Tschaggelar

Jan 1, 1970
0
Hi,

I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?
Yes, the 8038

Rene
 
A

Ancient_Hacker

Jan 1, 1970
0
Hi,

I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?

Thanks a lot

Joseph Zammit
Malta

need a bit more info:

variable over what frequency range? Continuously variable? By ranges?
Down to 0.001 Hz?

How stable in amplitude and frequency? How good a sine wave? What
percent distortion? What output voltage? What kind of load?
 
J

John Woodgate

Jan 1, 1970
0
In message said:
=====================================
I recall Mr Hewlitt and Mr Packard made a Very Able sine wave
oscillator back in the day... in Palo Alto as I recall....
Yes, but amplitude control by incandescent lamp is possible with
valves/tubes, but not with normal op-amps.
 
K

Ken Smith

Jan 1, 1970
0
You can do it with one op-amp that has a gain well over 3 at 100 kHz.
Google for 'Wien Bridge'. The problem is not getting it to oscillate but
controlling the amplitude so you don't get a clipped sine wave. There
are many ways of doing it; the best, but costly, is a vacuum thermistor
bead. You can use a FET as a voltage-controlled resistor.

Wien bridges aren't super easy to control the frequency on. A quad
op-amp version of the 3 opamp "state variable" oscillator may be a better
option for the OP.

I will even try to ASCII art draw it

R1 /+!---GND
---/\/\--+---< !
! ! \-!--
! ! R3 !
! ---/\/\--+
! R2 !
+--/\/\--+---/\/\/--
! ! R4
+---!!---+
! C1A ! C1B
R5A ! ! ---!!---
--/\/\-+-!-\ ! R5B ! !
! ! >---+----/\/\----+-!-\ !
! GND--!+/ ! >---+
! GND-!+/ !
! ---/\/\---+----/\/\----------------
! ! R6 ! R7
! ! /-!----
--+-< !
\+!---GND


Normally:

R6 = R7

R1 > 5*R5

R2 = 0.8 * R1

R3 = 1.3 * R4

R5A and R5B can include a POT like this:


----
!
\
/ <---/\/\---
\
!
GND
 
J

John Woodgate

Jan 1, 1970
0
dated Wed said:
Wien bridges aren't super easy to control the frequency on. A quad
op-amp version of the 3 opamp "state variable" oscillator may be a
better option for the OP.

Indeed, it's better but not 'simpel', which was the spec.
 
F

Fred Bartoli

Jan 1, 1970
0
John Woodgate said:
Yes, but amplitude control by incandescent lamp is possible with
valves/tubes, but not with normal op-amps.

Never seen an opamp Wien bridge controled by incandescent silicon?
 
J

John Woodgate

Jan 1, 1970
0
In message <[email protected]>, dated Wed, 16 Aug
2006, Fred Bartoli
Never seen an opamp Wien bridge controled by incandescent silicon?
No, I use a current-limited power supply. For incandescent silicon, you
need 1 kW audio amplifiers, or 5 kW lamp dimmers.
 
J

Jim Thompson

Jan 1, 1970
0
Indeed, it's better but not 'simpel', which was the spec.

For oscillators my gyrator BP works best... behaves just like a real
tank.

...Jim Thompson
 
N

Nico Coesel

Jan 1, 1970
0
Hi,

I need to design a simple variabel sine wave generator up 100kHz. Does
anyone know of single chip solution? If nt any ideas how to design one
with minimal chip count?

A microcontroller with an 8 bit (R2R) DAC.
 
K

Ken Smith

Jan 1, 1970
0
Fred Bartoli said:
Never seen an opamp Wien bridge controled by incandescent silicon?

I work with someone who invented the "light emittng PROM". Way back when
EPROMs had a window so you could erase them with UV.
 
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