# Astable Multivibrators/Oscillators

• ckaiser813
In summary, The task is to design an astable multivibrator with an output frequency of 5KHz and a duty cycle of 70%. The period of the output signal can be found using the formula T= 0.693 [(Ra+2Rb)C1]. The relationship between frequency and period is f= 1/T. The high and low values can be calculated using the formulas high = 0.67 (Ra*C) and low = 0.67 (Rb*C). These formulas can be found on pages 4 and 8 of the link provided. The values for Ra, Rb, and C1 can be determined using the given frequency and duty cycle.
ckaiser813
I have a very confusing teacher for my electronics lab, I am suppose to design an astable multivibrator with an output frequency of 5KHz and a duty cycle of 70% using a 555 timer.

Thats what I'm suppose to do in lab I have the following pre-lab questions that I can't find information for...

What is the period of the output signal? Give your answer in microseconds.

I have this formula T= 0.693 [(Ra+2Rb)C1] am I suppose to use the following frequency formula to find the values of Ra, Rb and C1. f0=1.44/(Ra+2Rb)C1 if so I don't understand.

The other questions have to deal with how long should the high be for each cycle and how long with the low be for each cycle, I can't even find a formula for that in my textbook.

Any help would help. Thanks

ckaiser813 said:
What is the period of the output signal? Give your answer in microseconds.

What is the relationship between frequency and period. If you know the frequency is 5 kHz, what is its period?

Take a look at the link below, particularly page 4 - Astable Operation and page 8, Figure 9d Astable Timing. There are some inconsequential errors in the drawing. Rb is drawn as a short, it should be a resistor. t1 (OUTPUT HIGH) has an extra parent on the left side of Rb. Nevertheless, these formulas should give you everything you need.

http://williamson-labs.com/555-AN170.htm

f= 1/T I knew that part just figured to write the entire question,

i figure out that Ra= 100 and Rb= 94 and C1= 1 uf

so should I use the following formula for the high and low

high = 0.67 (Ra*C)
low = 0.67 (Rb*C)

## What is an astable multivibrator/oscillator?

An astable multivibrator/oscillator is an electronic circuit that generates a continuous output signal without the need for an external input. It consists of two amplifying elements (such as transistors or op-amps) connected in a feedback loop with a capacitor and two resistors. This circuit creates a square wave output with a constant frequency and no stable state.

## What is the purpose of an astable multivibrator/oscillator?

The main purpose of an astable multivibrator/oscillator is to generate a continuous oscillating signal for various applications, such as timing and clock circuits, signal generation for communication systems, and as a source for pulse width modulation. It is also commonly used in electronic music instruments and as a clock signal for microcontrollers and digital circuits.

## What are the advantages of using an astable multivibrator/oscillator?

There are several advantages to using an astable multivibrator/oscillator. Firstly, it is a self-triggering circuit, meaning it does not require an external input to generate an output signal. It also has a wide range of frequency and duty cycle control, making it versatile for various applications. Additionally, it is simple and easy to construct with only a few components, making it cost-effective and widely available.

## What are the limitations of an astable multivibrator/oscillator?

One limitation of an astable multivibrator/oscillator is that it is not suitable for applications that require a stable output frequency, as it produces a non-sinusoidal output with a varying frequency. It also has a limited frequency range, and the output signal can be affected by external factors such as temperature and supply voltage. Additionally, it can be prone to noise and signal distortion.

## What are some common types of astable multivibrators/oscillators?

The most common types of astable multivibrators/oscillators are the transistor astable multivibrator, where two transistors are used as amplifying elements, and the 555 timer IC astable multivibrator, which uses a specialized integrated circuit. Other types include the op-amp astable multivibrator, the RC phase-shift oscillator, and the LC tank oscillator. Each type has its own advantages and limitations, and the choice depends on the specific application requirements.

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