# Questions tagged [transistors]

The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor), UJT (Unijunction transistor) and MOSFET (FET, for Field Effect Transistor)

4,691 questions
Filter by
Sorted by
Tagged with
70 views

### How to turn on a 12V Buzzer when transistor is OFF in the given circuit using minimal components?

In the given circuit i need to add an alarm circuitry where the 12V buzzer is ON when relay/transistor is OFF. Please guide me how to connect the 12V buzzer with minimal additional components
169 views

### What is this circuit's purpose

The input is a current source (photomultiplier), and the output is connected to a charge amplifier (I belive). I tried to draw the schematics from the circuit board, but I don't know what the three-...
52 views

### Plotting impedance of an inductor and capacitor in series

The capacitor and inductor are in series, which means that the equivalent impedance of these two elements is $$Z_{LC}=\frac{1-\omega^2LC}{j\omega L}$$ So for the three cases I got the following ...
106 views

### Leads of a particular electrical component

Is lead the most common term used in electronics to indicate the number of connectible input/outputs that a component has? Are there other terms that are used ...
104 views

### PNP transistor switching and inductive load

I am designing a circuit to control a motorcycle horn (its operating frequency is 490 Hz, its resistance is 3 Ohm, and it consumes 1A on average as indicated by the power supply), and LED lights. The ...
99 views

### Problem in understanding transistor

I am high school student we are doing transistor in our class but I could'n understand the topic, I have read several answer on site both physics as well as electrical engineering stack exchange ...
59 views

### Draw the maginitude as function of frequency

The circuit is this one, it consists of two common emitter transistors simulate this circuit – Schematic created using CircuitLab Some of the components where given but the others I had to ...
52 views

### Finding the component value of PNP transistor

This is my circuit simulate this circuit – Schematic created using CircuitLab This is the way I tackled this problem:  U_{e2} = 12 - I_e \cdot R_e = 12 - (2.02 \cdot 2) = 7.96 \text{ V} ...
57 views

### Why does this BJT work as a switch in this logical-NOT circuit, no matter how I orient the emitter and collector?

I have built the following circuit (obtained from Electronics All-in-One For Dummies (For Dummies 2nd Edition)) It works quite well. When the the momentary button (normally open) is not pushed the ...
41 views

### How to properly implement a crowbar circuit to perform a fault injection / power glitch attack?

I am trying to implement a power glitch attack. This is a hardware attack in which for a very short period of time (order of nanoseconds) I remove the power to a processor, using a transistor, to ...
66 views

### Working principle of a MOSFET Transistor

I was just reading a blog entry regarding the power conflict of the Arduino and trying to understand everything, when I came to a point where I could not understand the working principle of the ...
14k views

### What could be the reason that this transistor gets too hot unexpectedly?

In the following circuit, for the transistor it can be calculated that: Vce=4.5V and Ic=170mA. I also implemented this on breadboard and measured almost the same quantities. The opamp is an LM324 and ...
37 views

### Calculate the potential and current in the transistor circuit

I'm stuck on a question where I need to calculate the potential Vx and the current Ix in the circuit below. I have managed to get some equations, but the question does not mention what the ...
153 views

### How to calculate Resistor needed in PNP Transistor Circuit

I am trying to calculate the resistor value I need to achieve 35mA in my circuit. Vcc is 5V. Can someone explain the values I need to find in the datasheet as well as formula to use to find the ...
35 views

### Finding and plotting the impedance

I have gotten some help from the community here and thus I have reached this. This is part of the circuit that I want to find the impedance simulate this circuit – Schematic created using ...
65 views

### relay switching troubles

I am trying to switch a pair of 12v relays with approx 750r coils using a circuit and pre-fabricated pcb that I was given. The idea is that one relay is on when the other is off. The control comes ...
45 views

### Buffer amplifier for DC-1MHz (discrete parts)

I would like to make a buffer amplifier from discrete parts (transistors) which is working from DC to 1MHz. I'm not able to google any schematic or tutorial or app note etc. Everything I found was ...
46 views

### LED Strip / Resistor Heater + Driver Circuit

For my astrophotography equipment, I need to construct a dew heater and a flat field generator. A dew heater is simply a bunch of resistors connected in parallel such that each resistor outputs about ...
80 views

### Why do NPN/PNP transistors need to use doped semiconductors for the 'N' region?

By my understanding, as long as the P layers are properly doped (to have fewer free electrons), the electrons could not flow between collector and emitter until the P is given a satisfactory level of ...
98 views

### Why we need two resistors to control the gate voltage of a PUT transistor?

Looking the follow schematics you can see two resistors 15k and 27k that are controlling the gate voltage of the PUT (programmable unijunction transistor) transistor. My question is why we need two ...
70 views

### Of the millions of transistors in a typical microprocessor, what percentage of them are BJTs and MOFSETS?

This is broad in the sense of which microprocessor I am referring to. I expect them to be similar, but if not, then how about in an Intel 7th gen CPU and in an A11 iPhone chip? And what about how ...
46 views

### How the capacitor charges in this circuit?

I have been working on a kind of edge detector, and I would like to be guided about how the capacitor will charge in this circuit. when I don't have any transistor I could easily calculate the ...
61 views

### Transfer Function of two Common Emitters

I'm sorry about the pictures and used circuitlab. I am dealing with a circuit that has two common emitter transistors. Until now I was only dealing with a circuit that that is common emitter. This ...
69 views

### Transistor for 5V relay

Following up this question I need a transistor to switch the necessary current through the coil. I have some spare BC817 lying. My digital output pins can switch 5V@20mA. Do I need a base resistor to ...
37 views

### the transconductance of cascade MOSFET IF channel length modulation is NOT ZERO

What would the derivation of the cascode MOSFET transconductance in small signal analysis IF THE CHANNEL LENGTH MODULATION IS NOT ZERO, as most examples for the cascode mosfet transconductance say in ...
29 views

### PNP Highside Switch For Capacitive Sensor

Am wanting to use this Capacitive push button for a project but am having trouble understanding the application circuit. I understand that it is a PNP Highside switch and that current will flow to ...
41 views

### Reading recommendations to better understand how to understand the intended function of a circuit

This is a general question. Suppose I have a circuit like below from CircuitDigest: ￼ My supervisor said that about the circuit that.. [The] circuit does actually involve an amplifier, even ...
179 views

### Starting on electronics from zero - transistor timer

I'm just starting on electronics, trying to build a few circuits but can't understand properly how things work. I got this circuit and put on a breadboard, but the power source I have is 5V instead ...
49 views

### How to project a FET transistor as an amplifier?

I am trying to solve a problem on using an FET transistor as an amplifier with the common source configuration. The model should be appropriate for high frequencies. The problem gives the equivalent ...
43 views

### Transistor is not switching-Raindrop sensor with LED (Later Buzzer will be used)

I am creating a small application in which on detecting the water the Buzzer will ring. But right now I am testing with LED instead of Buzzer. Raindrop Sensor datasheet link: https://components101....
42 views

### Find DC components of npn and pnp transistor

I'm sorry but I can't seem to figure this transistor question. The question goes as follows: Draw a DC-circuit and determine the unknown component values. Which DC-voltages ( reference is ground) ...
49 views

### Role of input resistance in LM384 Audio Power Amplifier

let's consider the LM384 Audio Power Amplifier (here the datasheet) Can you explain me why is there the 150k resistance? It lowers the device input impedance, which is not good for a voltage ...
648 views

### How do we create current sources?

Constant current sources (simply, current sources) are useful and necessary devices. They are widely used to drive LEDs, charge capacitors and batteries, to bias differential amplifiers, etc. The only ...
153 views

### Amplifying photodiode current with BJT transistor

I'm trying to develop a kind of light detector. To do that, I'm going to use a photodiode and a bjt transistor to amplify its current. I found a circuit in this tutorial: which explains how the ...
59 views

### Using Thevenin Theorem to solve for unknown values in BJT voltage divider circuit

Assuming this is a DC bias of a voltage-divider type BJT circuit: V_CC = 10V Beta value = Not Known V_BE = 0.73V (Base-emitter voltage) And the Thevenin circuit ...
79 views

### Determine the transfer function using these values (Capacitors)

This is my circuit. simulate this circuit – Schematic created using CircuitLab These are the values of the components Determine the transfer function using these values This is what I ...
80 views

### Should I count transistor power while transistor is switching?

When transistor (bipolar transistor in common emitter amplifier) is closed (not conducting) or opened saturated (enough base current, collector current is limited by the resistance of the load), it ...
74 views

### Determining the component values for Dc

Draw the circuit diagram for DC and determine the component value. The transistor must be biased with : This is my attempt to solve this The picture bellow is the way I drew the DC circuit diagram ...
75 views

### What if I switch the place of the load in a common emitter NPN transistor circuit?

As you can see in the picture, there's an NPN transistor in a common emitter configuration. In the first configuration, the load is placed between the collector pin and Vcc, and it is the most ...
71 views

### Large Signal Transconductor

I have a basic question about the following circuit, which is introduced in the book " and is described as a "large signal transconductor": It says that: the capacitance value is chosen to be a ...
79 views

### Magnitude of a function with inductor and capacitor

I have a homework problem with the following circuit: I have solved the transistor biasing part and then drawn the AC-circuit of it. Then I need to find the transfer function. These are the ...
90 views

### How to connect a photovoltaic to a heating element directly

I am trying to connect a photovoltaic panel directly to a heating element (coil) without using a battery or an inverter and switch it on or off by using a transistor or a thyristor. I am well aware ...
34 views

### Power dissipation BJT transistor as voltage follower

Following the discussion from this thread I am finalizing my calculations. I am not sure that I am calculating the power dissipation correctly. Given the following circuit I need to operate the opamp ...
526 views

### MOSFET and BJT transistors

What is the main difference between a mosfet transistor and a BJT transistor. I know both are used for amplification and can be used as switches. But where would you use one over the other and what ...
174 views

### Simple Transistor Resistor Amplifier Circuit Question

Can Someone Please Help Me On Solving this. I have tried and stuck..In a point that can I apply Kirchhoff's Voltage Law around R2,R4 loop. simulate this circuit – Schematic created using ...
49 views

### Hows does this 12v relay works with transistor voltage drop?

I'm working my way through "Make: Electronics" by Charles Platt and came across the following schematic: As someone who just recently got started with electronics, what I can't wrap my head around is ...
110 views

### MOSFET-based ring oscillator not oscillating (but oscillate in simulator)

I created the following ring oscillator: In the LTspice simulator, it is supposed to oscillate at ~3Hz (LTspice source) given the 47nF caps and 680kΩ resistors: I then built this design on a PCB ...
64 views

### Finding the magnitude of the Transfer Function

This is the circuit, where some of the components values where given and the others, I found myself. (Sorry I have no link to the design, I needed membership there) The following part says to draw ...