what is this symbol?

Discussion in 'The Projects Forum' started by onlyvinod56, Feb 8, 2009.

  1. onlyvinod56

    Thread Starter Senior Member

    Oct 14, 2008
    Hi everyone,
    Iam attaching an image. just check it. what is that symbol?

    Iam also attaching a pdf file. How can the frequency of the output can be decided?
  2. Alexei Smirnov

    Active Member

    Jan 7, 2009
    Must be AND component with schmitt trigger on each input and inverted output...
  3. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    Since one input is always high, it is an inverter with a schmitt-trigger input.
    It is one gate of a CD4093 quad 2-input NAND Schmitt trigger IC.
  4. onlyvinod56

    Thread Starter Senior Member

    Oct 14, 2008
    okm thank you.

    How can i control the frequency with that IC?
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    Look up CMOS oscillators that use the inverter function. Fairchild Semi AN-118 is a nice source. It can be done with a single resistor, capacitor, and gate.

  6. SgtWookie


    Jul 17, 2007
    As AudioGuru suggests, it's likely a 4093 quad NAND Schmitt trigger; the Philips datasheet would be HEF4093B.

    Schmitt triggers are generally used to "square up" signals. Just looking at that one gate, the threshold levels for the inputs would be 1/3 Vdd and 2/3 Vdd.

    If the upper input were held high as shown, and the lower input started off low, the output would be high until the lower input exceeded 2/3 Vdd, or 8v. Then the output would go low until the lower input fell below 1/3 Vdd, or 4v.

    The NE566 function generator is a discontinued part. You'd have to use a different timer/oscillator IC; a 555 timer might be a substitute - but you couldn't use the 3.3v Zener or the rest of the oscillator circuit as shown.