Hello everyone,

now i want to use MAX038 to generate the triangular waveform with 2MHz. And i need your help.
At first i want to test the circuit in a simulator such as LTspice or TINA, so i need the spice model of MAX038. I have try to find it in Maxim website but there is no any more.Can anyone know where can i get the model of MAX038?
And the amplitude of MAX038 output is +-1V, and i need maybe +-50mv, so i need also to amplifier it. Do you know how?

Thanks a lot for your help in advance.
Jackie

 

The MAX038 is out of production since many years but you can still find on sale (e.g. on futurlec). Maxim doesn't have a spice model for it, I asked them before building my own signal generator with this IC.

However if you want to build a triangle wave generator you can set it up with a few op amps (a relaxation oscillator followed by an integrator) which is definitely a cheeper solution than using a MAX038 which can cost approx. 20 $.

To achieve the attenuation you request, use a inverting amplifier.
A voltage divider can do the job but the load can influence the output voltage so it's a bad idea.

simozz

 

And the amplitude of MAX038 output is +-1V, and i need maybe +-50mv, so i need also to amplifier it. Do you know how?

±50mV are very tiny, are you sure you want that values of voltage?
±50mV or ±50V?

If you need ±50V then you can see the totem pole circuit.

How is the frequency, fixed on 2Mhz or variable frequency?
If the frequency is fixed then you may check below link to be your reference.
triangular waveform with 2MHz using op amp

 

The MAX038 is out of production since many years but you can still find on sale (e.g. on futurlec). Maxim doesn't have a spice model for it, I asked them before building my own signal generator with this IC.

However if you want to build a triangle wave generator you can set it up with a few op amps (a relaxation oscillator followed by an integrator) which is definitely a cheeper solution than using a MAX038 which can cost approx. 20 $.

To achieve the attenuation you request, use a inverting amplifier.
A voltage divider can do the job but the load can influence the output voltage so it's a bad idea.

simozz

Hi Simozz,
Thank you so much for your help!
If i use MAX038, do you know where can i get the spice model of it?
If i don't use MAX038, do you know which circuit can i use to generate the triangular waveform with 2MHz, +-50mV?

Best wishes,
Jackie

 

±50mV are very tiny, are you sure you want that values of voltage?
±50mV or ±50V?

If you need ±50V then you can see the totem pole circuit.

How is the frequency, fixed on 2Mhz or variable frequency?
If the frequency is fixed then you may check below link to be your reference.
triangular waveform with 2MHz using op amp

Hi,
Thank you for your answer.
I need the +-50mV triangular wave as Dithering signal.The frequency is higher than 1MHz and variable.
Do you know any circuit to generate it, if MAX038 is not possible any more.
Thanks a lot.

Jackie

 

do you know where can i get the spice model of it?

As far as I know, it doesn't exist, there's no model available on internet, since Maxim doen't have one.
simozz

 

Hi,
Thank you for your answer.
I need the +-50mV triangular wave as Dithering signal.The frequency is higher than 1MHz and variable.
Do you know any circuit to generate it, if MAX038 is not possible any more.
Thanks a lot.

Jackie

Hi,

This sounds like an ADC project perhaps?

There are several circuits online that generate a triangle, maybe someone can post one here. They basically use a comparator and op amp integrator to generate a triangle. The frequency is variable via change of resistance or capacitance. I dont know if you need voltage control instead but you might provide more info about what this is to be used for.

 

What is the dither voltage being applied to? Generating an approximation of a 2MHz triangle will be far easier than generating an accurate triangle.

 

This sounds like an ADC project perhaps?

If you using ADC then how 2Mhz become digital?
If you using DAC, the output is 2Mhz then how is the input frequency?

 

As far as I know, it doesn't exists, there's no model available on internet, since Maxim doen't have one.
simozz

Exar might still do waveform generator chips - but I haven't checked.

 

You want to make a 2 Mhz, 50 mv P-P triangular wave? Just make one of these oscillators and follow it with a single pole RC filter. That should give you a beautiful triangular waveform for less than US$1.


Edit: If you use 11k and 1000 pf you will get a P-P output that is approximately 1% of the power supply voltage (50 mv P-P with a 5.0 V supply) or 5.6k for 2%. That should give you an idea of how to modulate the amplitude should you wish to do so.

 

You want to make a 2 Mhz, 50 mv P-P triangular wave? Just make one of these oscillators and follow it with a single pole RC filter. That should give you a beautiful triangular waveform for less than US$1.
View attachment 135267View attachment 135268View attachment 135270

From distant memory - I think the 038 the TS wants to use is "revving to valve bounce" at 2MHz. And the Maxim part is an "enhanced" copy of the original 8038 part.

 

Hi,
Thank you for your answer.
I need the +-50mV triangular wave as Dithering signal.The frequency is higher than 1MHz and variable.
Do you know any circuit to generate it, if MAX038 is not possible any more.
Thanks a lot.

Jackie

How is the frequency range, exp : 0~2Mhz, 200Khz~2Mhz?
Did you see the links that I made in the #3 -- triangular waveform with 2MHz using op amp.
Is this a homework or just your personal hobby?

 

Reference quote:
MrAL said: "Perhaps to be used with an ADC?"

If you using ADC then how 2Mhz become digital?
If you using DAC, the output is 2Mhz then how is the input frequency?

Hi there Scott,

Well a triangle wave could be used as a well controlled ADC dither source.

 

Reference quote:
MrAL said: "Perhaps to be used with an ADC?"

Hi there Scott,

Well a triangle wave could be used as a well controlled ADC dither source.

How is the input signal of your "A" in ADC?
How does the D(maybe 8 bits or more bits) become triangle wave, are you trying to use another DAC or use like R-2R ladder circuit?

 

How is the input signal of your "A" in ADC?
How does the D(maybe 8 bits or more bits) become triangle wave, are you trying to use another DAC or use like R-2R ladder circuit?

Hi again Scott,

The triangle would be used to dither the input to the ADC and thus would be one way to achieve practical oversampling. The triangle is mixed with the normal ADC input.

 

Hi again Scott,

The triangle would be used to dither the input to the ADC and thus would be one way to achieve practical oversampling. The triangle is mixed with the normal ADC input.

Could you draw a block diagram to show your idea?

 

Could you draw a block diagram to show your idea?

Hi,

Well, the only difference is that a low level triangle is added to the normal ADC input which is the input to be measured, and the output of the summer goes to the ADC. It's that simple of a block diagram.
So nothing changes but we add:
1. A low level triangle.
2. A summer, such as with an op amp.

 

See

 

See
View attachment 135432

He said that the frequency is variable and up to 2 Mhz, the range of frequency hasn't answer yet.