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TINA/Spice/SN74AC14: TINA/Spice/

Part Number: SN74AC14
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

How can I change the delay between the output of the inverter using a control voltage?

I know the frequency changes with a change in supply voltage but the delay still remains constant. Moreover, the propagation delay depends on the components itself.

So, is there a way of changing the delay between the output of inverters by adding any extra components?

  • Hi Jatin,
    You're right - the delay in your oscillator circuit is primarily derived from the RC delay added to the feedback loop. To change the oscillation frequency, you can either change the resistance R2, or the capacitance C3. The internal values will also have an impact, but nowhere near as much.

    What you're describing is a voltage controlled oscillator (VCO), and what you need to achieve it with your current circuit is either a way to change R2 or C3 with a voltage. The inverter's output resistance is typically much smaller than the external resistor, which is why you won't see a huge difference when changing Vcc (although Vcc changes _do_ affect the output resistance of the inverters - larger supply = smaller resistance).

    You can setup a set of resistors that are switched into the circuit depending on an input voltage via a comparator ladder, but that's not particularly efficient and will have discrete frequency steps. You can also use a reverse biased diode as a capacitor -- the amount of voltage on the diode will change its effective capacitance.

    There's no simple way to do this with just logic gates.