Clock Generator Circuit Using NAND Gates - Complete Guide

Lolita July 17, 2011

Learn how to build an accurate clock generator using NAND gates (IC 4011 CMOS or 7400 TTL). Includes circuit diagrams, frequency calculations, and practical tips for electronics projects.

Clock Generator Circuit Using NAND Gates

NAND Gate Clock Generator Circuit

1. Working Principle

This circuit uses two NAND gates configured as an oscillator:

R1 and C1 determine the frequency
The third gate buffers the output
Works with 5-15V (CMOS 4011) or 5V (TTL 7400)

2. Basic Circuit Diagram

 +Vcc
  |
  R1 (100K)
  |-----> Gate 1 (Input A)
  |
 C1 (10nF)
  |
 GND

Output: Gate 3 (pin 3 on 4011)

3. Frequency Calculation

Approximate formula:

f ≈ 1 / (2.2 × R1 × C1)

Examples:

R1=100K, C1=10nF → f ≈ 454Hz
R1=1M, C1=100nF → f ≈ 4.54Hz

4. Component Selection

Component	Value Range
R1	10KΩ - 10MΩ
C1	100pF - 47μF
Power	5-15V (CMOS)

5. IC 4011 Pinout

  ___ ___
1|   U   |14  Vcc
2|       |13
3|       |12
4|       |11
5|       |10
6|       |9
7| GND   |8

6. Practical Applications

Clock source for 4017 counters
Circuit timing control
Test signal generator
Educational digital systems

7. Implementation Tips

✔ Use ceramic or polyester capacitors for better stability
✔ Add a 1MΩ potentiometer in series with R1 for fine tuning
✔ Include an output buffer for heavy loads

Precision Variation

For more stable output:

Replace R1 with 1MΩ potentiometer + 100K resistor
Use polypropylene capacitors for critical timing

Pro Tip: This simple yet effective circuit is perfect for learning digital electronics. The CMOS version (4011) offers wider voltage range than TTL (7400).

Need higher stability? Consider crystal oscillator circuits!