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Old 1st April 2005, 09:59 PM   #11
trihieu is offline trihieu  United States
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Hey Hdoggz,

Can you tell me the values of the resistors?
Thank you very much.
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Old 2nd April 2005, 10:06 AM   #12
trihieu is offline trihieu  United States
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Hey sovadk,

In the circuit that you have, the other end of C26 connected to ground? Or is it something else?
Thanks
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Old 2nd April 2005, 06:11 PM   #13
sovadk is offline sovadk  Denmark
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C26 is a part of a high pass filter, used to shift the DC level of the triangle wave, before feeding the pwm comperators. It plays no role in the triangle generator.
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Old 4th April 2005, 12:04 AM   #14
sovadk is offline sovadk  Denmark
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I've done some simulations on my schematic. I've added a outbuffer to improved linearty and output impedance.

This is the result:

Click the image to open in full size.
Click the image to open in full size.

I've alos attached the orcad/pspice files for those of you who want to play arround with it.
Attached Files
File Type: zip triangle.zip (56.1 KB, 233 views)
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Old 4th April 2005, 05:21 AM   #15
hdoggz is offline hdoggz  United States
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trihieu,

The two equations in my previous post determine the value of the resistors and caps based on the frequency and amplitude ofthe triangle wave you want. I think once you solve them, you have more unknowns than equations which is a good thing cuz that means you can start off by choosing the value of one of the resistors. I'd start with something like 10k for 'R' to keep the current low. also, you may want to simulate thewhole thing in P-Spice before actually building it to doublecheck everything. again, use really highspeed components
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Old 4th April 2005, 04:35 PM   #16
trihieu is offline trihieu  United States
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Thank you so much guys.
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Old 4th April 2005, 08:16 PM   #17
trihieu is offline trihieu  United States
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sovadk,

What components are E4 and U1? I'm trying to buy those 2 components to build the circuit, but dont know what those are. Could you please help me out?
Thanks
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Old 5th April 2005, 12:25 AM   #18
sovadk is offline sovadk  Denmark
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E4 together with R9 and C3 is just working as a comperator. I've placed a picture earlier in this thread, showing the actual configuration. You can brobably use LM119, LM219, LM319 or some other cheap comperator. Be aware that those comperators need a pullup resistor to work, since they have a open drain configuration. I don't know why so many conperators are made with a open-drain configuration. It really limits their rise time, and increese the current if you go for a small pullup resistor.

U1 and V3 are used to trigger oscillation in pspice and are not needed IRL. Pspice starts a simulation by calculating DC bias points. If the circuit isn't triggered by something, I'll stay in that initial state forever.

If you are going to buy some resistors for this circuit, you won't have to go for the exact values. I believe that I've chosen values from the E24 range.

The ratio between R7 and R8 controls the hysteresis voltage on the comperator. In other words the amplitude of the triangle wave.

Q1 and Q2 are current generators. The resistors arround these transistors contorls the current, which controls the slope of the triangle wave.

C1 is charged by alternately by Q1 and Q2, where dU/dt=I/C. Thereby C1 also contorls the slope of the triangle wave.

The frequency of the triangle wave is a function of the slope and the hysteresis voltage.

Q5 together with R13 is just a simple voltage follower. The triangle wave is only linear if there are no resistive loads to C1, which will give the slope an exponential character.

V2 can be made with a simple decoupled resistive voltage divider.

I believe that Orcad has a free limited version of capture and pspice, if you would like to simulate the circuit that I've attached.
That should be about all there is to say for now.

Good luck with it.

Kaspar Sinding Meyer
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Old 15th October 2013, 11:20 PM   #19
tbj is offline tbj  United Kingdom
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Quote:
Originally Posted by sovadk View Post
C26 is a part of a high pass filter, used to shift the DC level of the triangle wave, before feeding the pwm comperators. It plays no role in the triangle generator.
Hi,

Sorry to bump an ancient thread, but if you are still active on the forum I would love to see this schematic if you still have it - The original image links do not work and I don't have the software to open your schematic file that you posted.

I think I know the general principle of your design as I have designed a triangle generator using a Schmitt trigger made up of two comparators and an RS flip flop and two current sources made out of discrete BJTs, but I'd like to see how you approached the problem before I go ahead and build it.

Currently trying to go up to a 500kHz clock in my amp but I am having a 'mare of a time generating a clean triangle waveform at this frequency.

How did the circuit perform and what frequency did you use?
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