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

Discussion in 'General Electronics Chat' started by saad.zafar01, Dec 15, 2012.

  1. saad.zafar01

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    Dec 15, 2012
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    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.....
     
  2. KMoffett

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  3. saad.zafar01

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    cant a sawtooth wave be generated by counters?
     
  4. KMoffett

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    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
     
    Last edited: Dec 15, 2012
  5. ScottWang

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  6. saad.zafar01

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    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%..
     
    Last edited: Dec 15, 2012
  7. saad.zafar01

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    @ScottWang please can i get the circuit diagram as i am totally new to this and have very low knowledge on this...
     
  8. saad.zafar01

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    also i have to use all ttl ICs
     
  9. ScottWang

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    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.
     
    Last edited: Dec 15, 2012
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  10. Papabravo

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    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.
     
  11. crutschow

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    That's a curious limitation. Is this some type of homework?
     
  12. Audioguru

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    Only school kids use antique TTL ICs today.
     
  13. saad.zafar01

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    the 74LS93 ic u told me about cant count upto 215 as i need the counter to count upto 215.
     
  14. ScottWang

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    You have to use two 74LS93 in series.
     
  15. saad.zafar01

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    how can i do that please elaborate.
     
  16. ScottWang

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