BJT Astable Multivibrators

Posted on Feb 4, 2014

The basic bipolar transistor (BJT) version of an astable multivibrator as shown in Fig. 4. 1. 1 has two outputs that repeatedly change state at a rate determined by the time constants of its feedback network. Although largely superseded by its equivalent op amp or timer IC versions in many applications, it is still a useful and flexible design for s

Click here to download the full size of the above Circuit.

quare wave and pulse generation. The circuit switches continuously from one state (TR1 on and TR2 off) to the other (TR1 off and TR2 on) and back again at a rate determined by the RC timing components Cl/R2 and C2/R3. The circuit produces two anti-phase square wave signals, with an amplitude almost equal to its supply voltage, at its two transistor collectors as shown in Fig 4. 1. 2. Suppose that at switch on, TR1 is conducting heavily and TR2 is turned off. The collector of TR1 will be almost at zero volts as will the left hand plate of C1. Beause TR2 is turned off at this time, its collector will be at supply voltage and its base will be at almost zero potential, the same as TR1 collector, because C1 is still un-charged and its two plates are at the same potential. C1 now begins to charge via R2 and its right hand plate becomes increasingly positive until it reaches a voltage of about +0. 6V. As this plate of the capacitor is also connected to the base of TR2, this transistor will begin to conduct heavily. The rapidly increasing collector current through TR2 now causes a voltage drop across R4, and TR2 collector voltage falls, causing the right hand plate of C2 to fall rapidly in potential. It is the nature of a capacitor that when the voltage on one plate changes rapidly, the other plate also undergoes a similar rapid change, therefore as the right hand plate of C2 falls rapidly from supply voltage to almost zero, the...

Visit page

Leave Comment

characters left:

Related Circuits

12V Battery Checker Circuit

This is a 12V battery checker circuit that uses 3 LEDs that light up at their respective voltages. The red LED lights up when the battery voltage is between 8 to 10V, the orange one at voltages...

230V Flasher Circuit diagram

This circuit operates with 230v. you can use this circuit to decorate your parties. I think this will be a wonderful circuit to you all. Here DIAC ER 900 and Triac BTW 11-400.

Automatic light activated switch circuit

The circuit can be used for switching OFF a particular lamp or group of lamps in response to the varying ambient light levels. The unit once built can be used for switching OFF a lamp when dawn...

BC548 Heat Sensor Diagram Circuit

Heat sensor circuit can be used to control any device using heat sensor. In this circuit a thermistor and a resistance is connected in series. This arrangement makes a potential divider circuit....

GSM CELL PHONE JAMMER SCHEMATIC

A wonderful diy gsm jammer or cellular mobile phone jammer schematic diagram for use only in GSM1900 with frequency from 1930 MHz to 1990 MHz. The GSM1900 cellular cell phone network is made use of...

Biosensor circuit

This week was spent completing a number of different objectives. Firstly, the software was downloaded to design the schematic for the circuit to be translated onto a PCB. Much of the week was spent...

Instrumentation circuit

The mechanical chassis prototype, as can be seen from the image on the left, was made using two materials: foam and aluminium. Foam was chosen due to its easy manipulation and aluminium due to its...

Hum Circuit

Although our kit utilizes an off-the-shelf microcontroller (AtMega328P-PU based Arduino), we additionally designed a simplified version. This allows other collaborators and students to potentially...

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Timer and Interrupt

There are 4 timers in PIC18 which are timer0 to timer3. Timers are used when precise timing event...

Mp pulse width control

Differential multiplexers are generally used in process control applications to eliminate errors...

Rf probe for vtvm

This circuit combines a 555 timer with a 2N2222 transistor and an external potentiometer. The pot...

Two sirens sound with ic 555

Operation of the circuit. Circuit is divided into three parts: low frequency production. The...

The MSC1210 Typical External Reset Circuit Schematic

and Flash Memory schematic that can be done from the following sources: power-on reset, external...

how to make simple earthquake sensor

The article shows a circuit idea which incorporates an innovative way of detecting the minutest...

Video Tracer For Trouble-Shooting

This circuit was designed as an aid to installers and maintainers of video systems. It is...