NOT, NAND Gate Frequency Calculator

Here we will learn how to use a NAND Gate Oscillator Calculator using CD4011 or any CMOS NAND gate IC.

This calculator will take values of:

• R = timing resistor (in ohms)
• C = timing capacitor (in µF)
• and give you:
• Output frequency in Hz
• Time period
• ON time
• OFF time (assuming 50% duty cycle square wave for simplicity).

Here is how this NAND oscillator actually works. We take two NAND gates from a 4011 IC — like pin 1-2-3 and 4-5-6 — and connect them in a way that they keep toggling the output ON and OFF rapidly.

Circuit Wiring Details

First we take a 4011 NAND gate IC which has 4 gates inside.

We use 2 gates only for this oscillator, one gate to make the feedback oscillate and the second gate to buffer or invert it for clean square wave.

Now connect it like this:

• Pin 1 and 2 (inputs of 1st NAND) → tied together
• A resistor (R) → goes from pin 3 (output of 1st NAND) back to pin 1/2
• A capacitor (C) → goes from pin 1/2 to ground

This forms a delay feedback loop. When power is ON, capacitor charges through resistor and changes logic at inputs, which changes output, which again discharges the capacitor. This keeps flipping the state like a seesaw.

Then we take pin 3 (oscillating output) and feed it to another gate input, like pin 4 and 5 tied together, so output at pin 6 gives you final clean square wave.

Frequency Formula We Used

We used the standard NAND oscillator timing formula:

f = 1 / (1.38 × R × C)

• R in ohms
• C in farads
• Result will be in Hz
• ON and OFF times assumed 50-50, so:

ON = OFF = 1 / (2 × f)

Example

Say:

• R = 100k
• C = 0.1 µF

Then:

f = 1 / (1.38 × 100000 × 0.1e-6) ≈ 72.46 Hz

So output blinks around 72 times per second.

Notes:

• Do not go too low with resistor or cap, IC might heat or output become messy.
• Always use ceramic or MKT cap (not electrolytic).
• Works from 5V to 15V (best at 9V or 12V).
• You can use all 4 gates for more buffering or logic expansion.

NAND Gate ICs (Standard + Schmitt Trigger)

The above calculator can be used for all the following ICs to calculate the frequency output of their oscillator configuration:

if you are building a simple RC oscillator then CD4011 and CD4093 are the kings. TTL ones like 74LS00 work but eat more power and glitch more often. 4093 is safest if you are going serious.

NOT Gate ICs (Inverters)

These ICs can be used in NOT gate oscillator configuration, where:

• R connects from output to input
• C goes from input to ground
• Output gives square wave

For NOT gate oscillator, always go with CD4069UB or CD4049UB, since they give perfect square wave even with high resistor/cap values. TTL ones like 74LS04 work only if you keep frequency high and R low.

Avoid These ICs for RC Oscillators:

Best Choices for Reliable Oscillator