The CD4047B CMOS multivibrator is a widely used timing IC known for its ability to generate accurate pulses and stable square wave signals. This article will discuss the CD4047B basics, pinout details, ordering variants, internal block diagram, specifications, features, working operation, applications, and comparison with CD4047.

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CD4047B CMOS Multivibrator Basic

The CD4047B is a CMOS multivibrator IC designed for accurate timing and waveform generation. It operates in both astable (free-running) and monostable (one-shot) modes, delivering stable pulse outputs with support for positive and negative edge triggering, including retriggerable operation.

The CD4047B is an improved version of the CD4047, offering better electrical performance, enhanced noise immunity, and wider operating voltage range due to its buffered CMOS design. It also provides more stable timing characteristics and improved reliability compared to the original version.

In astable mode, it produces continuous square waves, while in monostable mode it generates a single pulse based on external RC components. It includes complementary outputs (Q and Q̅), external reset, and trigger inputs for flexible control.

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CD4047B CMOS Multivibrator CAD Models

CD4047B CMOS Multivibrator Pinout Details

CD4047B Ordering Variants

Alternatives & Equivalent Model

• HEF4047B

• HCF4047B

• MC14047B

• TC4047B

• CD4047BE

CD4047B Logic Block Diagram

The CD4047B logic block diagram shows how the IC generates timing signals using an internal multivibrator controlled by external components. The R (resistor) and C (capacitor) connected to the timing pins form the RC network, which determines the oscillation frequency or pulse width. These components feed into the low-power astable multivibrator, which is the core of the circuit.

The astable gate control section enables continuous oscillation when the astable inputs are activated. In this mode, the circuit produces a steady square wave that is internally processed by a frequency divider (÷2). This ensures stable and symmetrical output signals at the Q and Q̅ pins.

For single-pulse operation, the monostable control block works with the trigger inputs (+Trigger and −Trigger). When triggered, it generates a precise output pulse based on the RC timing. The retrigger control allows the pulse to be extended if additional trigger signals are received before the cycle completes.

The external reset input can override all operations and force the output to a defined state. Finally, the outputs include the oscillator signal and complementary outputs (Q and Q̅), providing flexible timing and waveform control.

CD4047B CMOS Multivibrator Specifications

CD4047B CMOS Multivibrator Features

Dual Operating Modes (Astable and Monostable)

The CD4047B supports both astable and monostable modes, allowing it to generate continuous square waves or single output pulses. This flexibility makes it suitable for precise timing and control operations using a single IC.

Edge-Triggered Operation

The device can be triggered using either positive (+Trigger) or negative (−Trigger) edge inputs. This enables accurate control of pulse generation based on signal transitions.

Retriggerable Monostable Function

The retrigger input allows the output pulse duration to be extended if additional trigger signals are received before the current cycle ends, improving timing flexibility.

External RC Timing Control

The timing period or frequency is determined by external resistor and capacitor components. This allows easy adjustment of output characteristics based on circuit requirements.

Complementary Outputs (Q and Q̅)

The IC provides both normal (Q) and inverted (Q̅) outputs simultaneously, making it useful for driving complementary circuits without additional components.

Built-in Oscillator with Frequency Divider

An internal oscillator generates signals that are divided by two, ensuring stable and consistent output waveforms with reduced frequency variation.

Wide Operating Voltage Range

The CD4047B operates over a wide supply voltage range (typically 3V to 18V), making it compatible with various digital and analog systems.

External Reset Capability

The external reset input allows the user to quickly reset the output state during operation, providing better control and reliability in timing circuits.

CD4047B Working in Circuit

The diagram shows the CD4047B operating in astable mode, where it generates continuous square wave signals without any external trigger. The astable inputs are enabled, allowing the internal multivibrator to switch automatically between HIGH and LOW states.

The oscillation frequency is set by the external RC network using R1 (560kΩ) and C1 (100nF). As the capacitor charges and discharges through the resistor, it controls the timing of the output signal.

The IC provides complementary outputs at Q (pin 10) and Q̅ (pin 11), along with an oscillator output (pin 13). These outputs produce stable and synchronized waveforms, with Q and Q̅ always inverted.