HELP NEEDED!! what IC should i use to generate sawtooth wave

Thread Starter

saad.zafar01

Joined Dec 15, 2012
19
hey.. im a newbie and i want help..
i want to know which IC to use to generate a sawtooth wave of magnitude 215 for a PWM circuit.....
 

KMoffett

Joined Dec 19, 2007
2,918
Yes. You would need a clock, a counter, and a DAC (digital-to-analog converter) chip. And probably a buffer opamp on the output
Are you saying you want a 215 level staircase output?

Ken
 
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Thread Starter

saad.zafar01

Joined Dec 15, 2012
19
yes i want a 215 level staircase output... i also have to give the user the choice to select the duty cycle from 12.5% , 25% , 32,5% , 50% , 62.5% , 75% and 87.5%..
 
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ScottWang

Joined Aug 23, 2012
7,397
NE555(OSC) → 74LS93(Counter) → DAC(8 bits DAC - DAC0808)

Do you have any reason why you want to use TTL?
I haven't try the TTL before, because I usually used the CMOS.
Maybe you can try 74HC93

search datasheet:
http://www.datasheetcatalog.com/

You can search the info of IC as above or on google.
Search on google "NE555 astable schematic" for NE555 circuit.
Search on google "DAC0808 schematic" for DAC0808.

After you got the all infos, then you could try to draw them together.
 
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Papabravo

Joined Feb 24, 2006
21,159
You can use an operational amplifier configured as an integrator. Put a square wave in and you get a triangle wave. To get a sawtooth you "periodically "reset" the integrator. This can be done in several ways.

Choosing the "reset" time you can set the voltage to be identical to the DAC approach.
 
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