Triangle Wave Design

[David Grant]

I need, if possible, a fairly accurate 300kHz triangle wave generator design
that outputs a signal which swings from 0-5V using only a GND and 5V power
supply. Before I go thinking about this too much, can someone tell me if
this is possible, or if there's an already existing design out there?

Thanks,

Dave

 

[Leon Heller]

"David Grant" <NO_SPAM_PLEASE_jmd_2003@msn.com> wrote in message
news:3wpTd.7619$RM2.7597@read1.cgocable.net...

I need, if possible, a fairly accurate 300kHz triangle wave generator
design
that outputs a signal which swings from 0-5V using only a GND and 5V power
supply. Before I go thinking about this too much, can someone tell me if
this is possible, or if there's an already existing design out there?

You could do this with a software DDS, using, say, an Atmel ATtiny2313
running at 20 MHz. See my web site for details of a 250 kHz DDS generator
using an 11 MHz '2313. Output is up to 2.56V, so you would need an amplifier
for 5V.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller

 

[Mac]

On Thu, 24 Feb 2005 14:01:21 -0500, David Grant wrote:

I need, if possible, a fairly accurate 300kHz triangle wave generator design
that outputs a signal which swings from 0-5V using only a GND and 5V power
supply. Before I go thinking about this too much, can someone tell me if
this is possible, or if there's an already existing design out there?

Thanks,

Dave

Well of course it can be done!

One very simple way would be to clock a counter up, then down, and feed
the count output to a DAC.

You could put the counter in a PLD.

If you use an 8-bit counter, then you have to count from 0 to 255, then
back down to 0, so that is 511 intervals.

The master clock would run at 300 kHz * 511 = 153.3 MHz, or however close
to that you can get. That is a pretty fast clock. So maybe you could just
use 6 or 7 bits to get the master clock speed down. You would put a
low-pass filter at the DAC output.

Another simple way would be to generate a 300 kHz square wave (using
logic) then feed it to an op-amp integrator. If needed, the integrator
could output a smaller triangle wave, and the output would then go to
another op-amp which would bring the signal up to the required 5 V
peak-to-peak swing.

Have fun.

--Mac

 

[Tony Williams]

In article <3wpTd.7619$RM2.7597@read1.cgocable.net>,
David Grant <NO_SPAM_PLEASE_jmd_2003@msn.com> wrote:

I need, if possible, a fairly accurate 300kHz triangle wave
generator design that outputs a signal which swings from 0-5V
using only a GND and 5V power supply. Before I go thinking about
this too much, can someone tell me if this is possible, or if
there's an already existing design out there?

You could vastly reduce the problems if you were
to first of all develop +10V and -5V supply rails.
That gives the headrooms to make the 5V triangle
generation much easier. Something like this.

+--|>|--+---/\/\----------------+
| D | R |
| |/e |
+5V--+-----|pnp |
|\ +10V |
| ______|______ |
<--Triangle---+ +5-|+Vref | |
| | | |
C +-----|Threshold | |
0v-----||----+ | Out|---+
+-----|Trigger | |
| | | |
| 0V-|-Vref_ ______| |
| | |
|/ -5V |
0V--+-----|npn |
| |\e |
| D | R |
+--|>|--+---/\/\----------------+

Inside the box is a discrete equivalent of the
555 circuit, two comparators and an R-S flipflop.

--
Tony Williams.

 

[mike]

David Grant wrote:

I need, if possible, a fairly accurate 300kHz triangle wave generator design
that outputs a signal which swings from 0-5V using only a GND and 5V power
supply. Before I go thinking about this too much, can someone tell me if
this is possible, or if there's an already existing design out there?

Thanks,

Dave

NO, It can't be done.

How accurate is "fairly accurate"?
Accurate how? Frequency? linearity? Symmetry? Pointy-ness of the peaks?
Glitches at the peaks? Harmonic content?
What's the min/max range of your 5V supply?
Do you really, really, really have to go from 0.00000000000V to
5.00000000000V?
Any reason you can't generate a smaller triangle and amplify it?

Figure out what you really need. Relax some of the numbers and
impossible might become trivial, maybe...
A CMOS 555 can make a nice triangle-looking waveform at amplitude Vcc/3.
Bottom half of an exponential is kinda linear...
mike

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[Ken Smith]

In article <4d42ace7c4tonyw@ledelec.demon.co.uk>,
Tony Williams <tonyw@ledelec.demon.co.uk> wrote:

In article <3wpTd.7619$RM2.7597@read1.cgocable.net>,
David Grant <NO_SPAM_PLEASE_jmd_2003@msn.com> wrote:
I need, if possible, a fairly accurate 300kHz triangle wave
generator design that outputs a signal which swings from 0-5V
using only a GND and 5V power supply. Before I go thinking about

Tony's design needs an op-amp to follow it and provide just a bit of gain
to bring the swing up to the required 0-5V

--
--
kensmith@rahul.net forging knowledge

 

[Fred Bloggs]

I need, if possible, a fairly accurate 300kHz triangle wave generator design
that outputs a signal which swings from 0-5V using only a GND and 5V power
supply. Before I go thinking about this too much, can someone tell me if
this is possible, or if there's an already existing design out there?

You don't need any such thing- just make the T-wave go from 0-2.5V and
scale the Vref to the other input of your PWM comparator with a resistor
divider-probably a 2:1 that is two equal valued resistors. Sheesh.

 

[Tony Williams]

In article <cvrb67$co0$5@blue.rahul.net>,
Ken Smith <kensmith@green.rahul.net> wrote:

Tony's design needs an op-amp to follow it and provide just a bit
of gain to bring the swing up to the required 0-5V

The Vrefs of 5v and 0v on the discrete '555' give
the required 5v pk-pk swing, but does need buffering.

I've been wondering whether it is possible to use
the oscillator itself to provide the required extra
supply voltages. Perhaps run an actual 555 off the
5v rails and provide just enough current to power an
opamp at greater than 0v and 5v rails.


5v---+---------+
| |
[1k0] [4k3]
| +---------------------[9k1]---+
| | |
e\| |/e 5v 5v |
pnp|--+--|pnp | | |
/| | |\ |C1 _| _ |
| | | === | 555 | |
+----+ | |680pF | | 5v |
| | | +--|Thr | |\| |
[1k6] +---+-------+ | Out|--| >--+
| | | +--|Trig | |/| |
+----+ | |C2 | |______| 0v |
| | | === | | |
\| | |/ |680pF | | |
npn|--+--|npn | | 0v |
e/| |e | | |
| | 0v | |
| +---------------------[9k1]---+
[1k0] [4k3] | |
| | |Triangle |
0v---+---------+ | 1.666V p-p |
\|/ |
+9Vdc approx->+------------------+--|<|--+ |
| 5v | | D | |
| | | ===0.1 | |
| [4k3] | | D | |
| | | 5v-+--|>|--+ |
+-[4k3]--------+ | | |
| |_ | | 0.1=== |
| / -|--+ | | |
Out<--+-------<Op | | | +--+
5v p-p \_+|--|-----+ |
| | 0.1===
| [4k3] |
| | 0v-+--|<|--+
| 0v | D |
| ===0.1 |
| | D |
-4Vdc approx->+------------------+--|>|--+

|\
--| >- =74HC non inverting buffers in parallel.
|/

2-off 0.43mA const-I sources switched on/off
alternately by the output sq wave. The sq wave also
drives the capacitor pumps to generate the extra
supplies for the output opamp.

--
Tony Williams.