DS

Here is a simple but effective intercom circuit that is based fully on transistors.The circuit is based on a three stage RC coupled amplifier. When the push button S2 is pressed, the amplifier circuit wired around T1 & T2 becomes an a stable multi vibrator and starts producing the ringing signals. These ringing signals will be amplified by the transistor T3 to drive the speaker. When the push button S2 is released the circuit will behave as an ordinary amplifier and you can talk to the other side through it. To construct a two way intercom, make two identical copies of the circuit given below and connect it according to the given connection diagram. The stand by current consumption of this circuit is around 20mA. Circuit Diagram Connection Diagram  

In general, different types of electrical and electronic components such as transistors, integrated circuits, microcontrollers, transformers, regulators, motors, interfacing devices, modules, and basic components are used (as per requirement) to design different electrical and electronics projects. It is essential to know about the working of each component before using it practically in circuit applications. It is very challenging to discuss in detail about all the important components of electronics in a single article. Hence, let us discuss in detail about junction field effect transistor, JFET characteristics, and its working. But, primarily we must know what are field effect transistors. Field Effect Transistors In solid state electronics, a revolutionary change was done with the invention of the transistor, and is obtained from the words transfer resistor. From the name itself, we can understand the way of functioning of transistor i.e., transfer resistor. The transistors are cla...

This is a unique flasher circuit employing a single driver transistor that takes its flash-rate from a flashing LED. The flasher within the photo is 3mm. An ordinary LED won't work. The flash rate can not be altered by the brightness of the high-bright white LED will be adjusted by altering the 1k resistor across the 100u electrolytic to 4k7 or 10k. The 1k resistor discharges the 100u in order that when the transistor activates, the charging current into the 100u illuminates the white LED. If a 10k discharge resistor is used, the 100u isn't absolutely discharged and therefore the LED doesn't flash as bright. All the components within the photo are within the same places as within the circuit diagram to make it simple to envision how the components are connected. The circuit uses a flashing LED to flash a super-bright 20,000mcd white LED

Warning: Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres. Circuit diagram Notes : I have used a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good results. I have used an ECM Mic insert from Maplin Electronics, order code FS43W. It is a two terminal ECM, but ordinary dynamic mic inserts can also be used, simply omit the front 10k resistor. The coil L1 was again from Maplin, part no. UF68Y and consists of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of wire greater than 2 feet may damp oscillations and not allow the circuit to work. Although RF circuits are best constructed on...

   4 Transistor FM Transmitter Circuit Diagram Build a  4 Transistor FM Transmitter Circuit Diagram. This 4 Transistor FM Transmitter Circuit Diagram provides an FM modulated signal with an output power of around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is limited by the 5k preset trim potentiometer.  The oscillator is a colpitt stage, frequency of oscillation governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. The output stage operates as a 'Class D' amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage.

Types of transistor Transistor circuit symbols There are two types of standard transistors,   NPN   and   PNP , with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon. This page is mostly about NPN transistors and if you are new to electronics it is best to start by learning how to use these first. The leads are labelled  base  (B),  collector  (C) and  emitter  (E). These terms refer to the internal operation of a transistor but they are not much help in understanding how a transistor is used, so just treat them as labels! A Darlington pair is two transistors connected together to give a very high current gain. In addition to standard (bipolar junction) transistors, there are  field-effect transistors  which are usually referred to as  FET s. They have differen...

Using only four transistors in the quasi-complementary amplifier configuration, this transistor power amplifier circuit can deliver 90W of power into 4 ohm loads and at low cost. As shown in the transistor power amplifier circuit there are no expensive components in this circuit, except the power transformers and speakers. As shown in the diagram there are no expensive components in this circuit, except the power transformers and speakers. Input stage is formed by this two current driver directly raised a pair of transistors of the output stage. Transistor level end (2N3055) mounted on a heat sink to keep the lifetime of these devices. Supported by one source (of 80Vcc) at the output of the final stage, before the speaker, a capacitor is placed to block DC current, and just skip the audio signal. The power supply circuit 90 W audio power amplifier must be sufficient to provide current 1.5A per channel audio. Thus the power required to operate the stereo 3A and 6A is required for the fo...

Warning: Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres. Notes I have used a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good results. I have used an ECM Mic insert from Maplin Electronics, order code FS43W. It is a two terminal ECM, but ordinary dynamic mic inserts can also be used, simply omit the front 10k resistor. The coil L1 was again from  Maplin, part no. UF68Y and consists of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of wire greater than 2 feet may damp oscillations and not allow the circuit to work. Although RF circuits are best constructed on a PCB, you can...

Mini 3 transistor amplifier is a simple amplifier with 50mW power drawn by 3 transitor. The series of three mini-amplifier transistors can be used for loud speaker 8 ohm load. Source voltage required to activate the mini-amplifier can be drawn from the batteries 9V.Rangkaian 3 transistor amplifier is often used in simple portabe audio devices such as radios or small tape recorder. Mini-transistor amplifier circuit 3 is quite simple as shown in the figure below. Mini-transistor amplifier circuit 3 includes type of amplifier OTL (Output Transformer Less). Mini-transistor amplifier circuit 3 is used for output coupling capacitors. Amplifier circuit is simple and suitable when used for audio amplifier experiment.

For a collector follower with emitter resistor, you’ll often find that the gain per stage is no more than 10 to 50 times. The gain increases when the emitter resistor is omitted. Unfortunately, the distortion also increases. With a ubiquitous transistor such as the BC547B, the gain of the transistor is roughly equal to 40 times the collector current (Ic), provided the collector current is less than a few milliamps. This value is in theory equal to the expression q/KT, where q is the charge of the electron, K is Boltzmann’s constant and T is the temperature in Kelvin. For simplicity, and assuming room temperature, we round this value to 40. For a single stage amplifier circuit with grounded emitter it holds that the gain Uout /Uin (for AC voltage) is in theory equal to SRc. As we observed before, the slope S is about 40Ic. From this follows that the gain is approximately equal to 40I cRc. What does this mean? In the first instance this leads to a very practical rule of thumb: that gain ...

Based on RDV and DragonFly's versions with mods

The above sequence is a circuit of development of the transistor circuit tester before, which of course added few more components , and resulting in even be better. Examiners transistor circuit above only knows his gain is only on the collector . In addition to well known techniques of data materials used therein . That is , if the elements germanium and the like which are in the tool is still functioning or vice versa. Part List : R1=330R/0,5W R2=27K R3=1K R4=1K R5,R6=5K6 C1=1uF C2=2,2uF Q1=Socket transistor T1=Transformator output (OT) S1=Switches friction G1=3V X1-1, X1-2=Speaker connector How to test : Emitter associated with foot condensator and resistor R4, Base is connected with one leg transformer OT , The Collector is connected to the foot of R2 and R3. If you hear a hiss , the sound in few seconds it still has not changed means that transistor still disqualify technical data.

Description  For a collector follower with emitter resistor, you’ll often find that the gain per stage is no more than 10 to 50 times. The gain increases when the emitter resistor is omitted. Unfortunately, the distortion also increases. With a ubiquitous transistor such as the BC547B, the gain of the transistor is roughly equal to 40 times the collector current (Ic), provided the collector current is less than a few milliamps. This value is in theory equal to the expression q/KT, where q is the charge of the electron, K is Boltzmann’s constant and T is the temperature in Kelvin. For simplicity, and assuming room temperature, we round this value to 40. For a single stage amplifier circuit with grounded emitter it holds that the gain Uout /Uin (for AC voltage) is in theory equal to SRc. As we observed before, the slope S is about 40Ic. From this follows that the gain is approximately equal to 40I cRc. What does this mean? In the first instance this leads to a very practical rule of ...