Two multivibrators operating at distinct frequencies can be constructed utilizing the NAND gates within a 4011 IC. When the output of IC1.B is positive relative to IC1.C, LED D1 illuminates. Since the states of IC1.A and IC1.D are precisely opposite, D2 remains lit when D1 is off, and vice versa.
Different Frequencies of the Oscillators
The oscillators operate at distinct frequencies determined by the values of R2/C2 and R5/C5, following the formula f0 = 1 ÷ (1.4 RC). With the specified component values, these frequencies are 2.2 Hz and 7.2 Hz, respectively. It’s essential to use low-current LEDs due to the limited current capacity of the MOS IC, which cannot handle the current requirements of standard LEDs.
Appropriate Resistance Values for Stable Operation
The series resistors R3 and R6 are tailored for a 12 V supply voltage, resulting in a circuit current consumption of approximately 5 mA. However, the 4011 can function across a voltage range of 5–15 V. If higher currents are needed, the HC family (operating at 3–6 V) or the HCT family (at 5 V) can be utilized. Notably, in the HC family, the quad gate IC’s part number is HC7400.
Understanding Multivibrator Circuits
Multivibrator circuits, essentially switching circuits, generate non-sinusoidal waveforms like square waves, rectangular waves, and sawtooth waves. They find applications as frequency generators, frequency dividers, time delay generators, and even as memory elements in computers.
Principle Behind Astable Multivibrator
The Astable multivibrator operates based on slight variations in the electrical properties of transistors. This disparity causes one transistor to turn on faster than the other when power is initially applied, triggering oscillations. There are three types of multivibrator circuits: Astable, Bistable, and Monostable. Among these, the Astable multivibrator is internally triggered, while the Bistable and Monostable types require external triggering mechanisms.
Triggering the Bistable Multivibrator
To alter the stable state of the binary system, an appropriate pulse must be applied to the circuit. This pulse attempts to drive both transistors into the active region, resulting in regenerative feedback that changes the state of the system.