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

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How to compensate for the diode drop in a common collector?

Everytime I need to bias one of my op amp circuits, I normally use a voltage divider feeding into a unity op amp buffer to achieve this. After reading this answer, I thought I'd try to simulate it. ...
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55 views

Keep volts the same but increase the amps in a 60hz 120v AC circuit

I have a over the range microwave with a built in fan for exhausting range fumes below. Would like to add an inline fan to it in the attic that matches the speed of the fan in the microwave but I ...
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1answer
79 views

What type of transistor would be required?

I am trying to turn on a 12V LED, whenever power is applied to a 3.5V LED. I want to use a switch transistor instead of a relay. With the relay, 3.5V+/- on the switch activates 12V passthru; what ...
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1answer
127 views

Properties of transitors used as diodes

Consider the NPN BJT. Normally, if you want to use it as a diode, you short base to collector and treat the emitter as the cathode. But in principle, you could also use the base emitter junction by ...
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1answer
62 views

H Bridge Control using Raspberry PI / Micro controller

I am looking for input on this circuit that I have designed. I am currently working on a project called the Net-EEL RC Car. It is an RC car that will be controllable using Network Socket Servers / ...
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1answer
77 views

why emitter is connected to high level and collector to low level?

generally, in all switching circuit, emitter is connected to ground and collector is connected to high level. i am not getting why is it so? is there any special purpose?
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1answer
53 views

Two different 3-AND gates: correct implementation?

One of the questions in my textbook (Introduction to Computing Systems) asks to design a 3-input AND gate. The given solution is as follows: simulate this circuit – Schematic created ...
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2answers
45 views

Help driving 9V circuit with a 5V RTC clock interrupt pin (active low)

I am using this RTC clock module (http://datasheets.maximintegrated.com/en/ds/DS3231.pdf). The DS3231 has alarm function that can be programmed twice a day. When the alarm goes off it makes the ...
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2answers
76 views

CMOS OR gate using 4 Transistors

Can an OR gate be implemented using 4 CMOS transistors? The circuit would have two n-type transistors in parallel in the pull-up network, and two p-type transistors in series for the pull-down ...
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1answer
49 views

Why a MOSFET in accumulation mode is not conducting?

In accumulation mode, the channel is not conducting, whereas in inversion mode it is conduting. But if in both cases I have free charge carriers in the channel, why isn't there conduction in both ...
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1answer
104 views

Unusual voltage drop at BJT (2N2222)

I'm using BJT (NPN) that is supplied with 7V DC signal at the collecter, 5V DC signal at the base and need a 12V output at emitter. Right now i'm getting 4.35V at emitter. How can i implement it?
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1answer
53 views

Phototransistor bandwidth issue

I'm trying to sense IR wave with a phototransistor circuit. The circuit operates well under DC operations (I mean 3V or 0V through inputs). However, if a square wave is supplied from UART input, ...
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60 views

how many transistors can be fitted into an IC by 1971 and what could be achieved by that [closed]

facts show that around 2300 transistors can be fitted in an IC by 1971 and moore's law can be used to predict the number of transistors in an IC. but what was the possibilities uncovered with this ...
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1answer
55 views

PSPICE Simulation of Cascode Amplifier Not Working

Can anyone please tell me why I am getting the following "floating node" errors. I have fiddled around with the resistors to see if it affects anything, so these are not the actual values. I have also ...
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0answers
31 views

Which company originated the transistors labelled as SSxxxx, such as SS8050, SS8550, or SS9011? [duplicate]

These are made by large number of manufacturers today so it's hard to figure it out just based on datasheets... If it's of any help, here are some links to datasheet collections for these: 8550: ...
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1answer
79 views

Can I use a single SPST switch and transistors to simulate a DPST switch for POS and GND wires to a load?

I am wanting to create a system that supplies approximately 24V and 1A to a load (essentially a resistor) for up to 1 second. The process will not be repeated for any one load and there would be no ...
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1answer
115 views

Is this use of optocoupler wrong?

This is nearly not exactly how the circuit looks like, but I have a feeling that this circuit could cause problems while working. My feeling is that initially as Q1 would be in ON position, the ...
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0answers
38 views

Common Drain Design Not Meeting Spec

I am trying to design a Common Drain amplifier with specifications below. I have reworked the problem over 10 times now and have not achieved anywhere near an appropriate solution. I have spelled out ...
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1answer
138 views

Trying to understand this oscillator… there's no emitter grounding or bias

I dissected and drew up this oscillator circuit from a cassette machine the other night. It's purpose is for biasing the tape. I'm curious though as to how this oscillator functions since the base is ...
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2answers
81 views

Determine the Number of Transistors Needed to Build CMOS circuit

I would like to determine the number of transistors that will be used in the CMOS circuit below. Is there a specific formula for it?
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2answers
100 views

Opamp Misbehaving in Constant Current Source Circuit

I'm planning to build a current regulator for a power supply and I'm prototyping a number of different regulator circuits. First up, the op amp and transistor circuit shown below. I felt I ...
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2answers
55 views

Mosfet time and PWM frequency relation

what is the relation that I have to take into account when I select a mosfet(or a transistor in general) for pwm driving about rise/fall/turn off delay/turn on delay and the PWM frequency? How to ...
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1answer
29 views

Proteus BJT Astable Multivibrator Simulation Error

I am pretty new in Proteus and made a simple flip flop circuit as shown below. When I run the simulation, the circuit does not work as intended. Both of the LEDs light up at the same time. (LEDs ...
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4answers
439 views

What do the arrows in transistor symbols point to (and from)?

Transistor symbols are often drawn with arrows pointing in one direction or the other, depending on type, like in the following symbols: But what is the arrow actually pointing at? And from where ...
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1answer
102 views

Solid-state relay realized with bipolar transistor

I'm searching information about SSR realized with bipolar transistor. Basically I need something like tutorial how they are constructed, how they work, what elements they contain etc... I searched in ...
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2answers
143 views

npn transistor common emitter [closed]

A microcontroller needs to be able to turn a 24V, 1 Ohm resistive load off and on. It has an output pin that can be set to either 0V or 5V. When the output is 0V, the load should be off, when 5V, the ...
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69 views

Analyzing a MOSFET amplifier circuit

This is the problem: And this is my solution: I want to check if it is correct or I've done some mistakes.
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1answer
98 views

Analyzing a MOSFET circuit

This is the problem: And this is my attempt to solve it: For (1): I don't know how to get vgs or how to use the hint to get rid of it. For (2): I assume that ...
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1answer
52 views

light dependent 5V switch

I wired up this light dependent switch which works fine. when in daylight and covered. how can i make it work when the light source is dimmer? ie is it a case of changing 1 of the resistors?
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2answers
373 views

What's the middle terminal in the VN2222 MOSFET?

In the VN2222 MOSFET below (diagram is from PSPICE), what is the terminal with the arrow pointing in? The one to the left is the gate, above and to the right is the drain and at the bottom is the ...
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2answers
64 views

Trying to find steady state

I'm taking my first course in electronic circuits and I'm a little lost when it comes to combining NMOS transistors with capacitors. In particular I am having trouble with finding the steady state for ...
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3answers
183 views

How do you calculate the current and voltage when the emitter is grounded for saturation mode

For example, assume you have this transistor with a grounded emitter: Since we are dealing with a saturation mode, \$v_{ce} = 0.2 \$ making the drop across the resistor 9.8 v. The current going ...
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2answers
66 views

RGB control with MOSFets

I would like to control RGB leds , or other PWN channels , using a micro controlelr, and ...
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1answer
57 views

Driving a 4.5V motor with PWM from an Arduino

This is a basic question but I would appreciate help. I have: An Arduino A 4.5V DC motor Various transistors, like BC337, 2N7000, 2N2222A What I'm trying to do is very simple: control the motor ...
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2answers
32 views

Question about the current flow and voltages in a simple NAND diagram

I've so far learned about boolean algebra and its applications to transistors. This is a picture of a NAND diagram: A NAND has this boolean property : \$ f(A,B) = \overline{A \cap B}\$. What I want ...
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3answers
72 views

Transistor with different voltage in colector and base

I have a small LED of 5mm and an arduino powered by 9V. When I connect the LED to Vin (9V) using a 330 ohm resistor the LED brights very high. When I connect the LED to 5V (from arduino) using a 330 ...
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3answers
116 views

The “AND” gate function

I am learning about the "AND" gate function in Navy school. What I know is that when a low voltage is at the base of Q1, the transistor is in cutoff mode since the collector is reading high (> 2 ...
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0answers
35 views

Function of diode-connected transistor [duplicate]

Can anyone explain to me how a diode-connected MOS transistor works especially intuitively?
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3answers
78 views

What is meant by pinch-off voltage? [closed]

When I read about junction field effect transistors I always get confused about pinch-off voltage in junction field effect transistors. Please explain what this is.
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2answers
106 views

Amplifier design with three stages

As a project for my electronics 101 class, I've been assigned to design a three stage amplifier using bjt transistor to achieve a gain of 150 and input resistance of 100k and output resistance of 50 ...
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3answers
65 views

Do we want output resistance of a transistor to be high or low

I have a serious doubt about output resistance of transistors. We say that output resistance of a device must be high, for example in BJTs, because it is actually a norton resistance in parallel with ...
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2answers
165 views

How does this circuit give DC output?

I don't understand how this circuit works. I'm not sure if it's correct. It should give a DC output, but how would it do that?
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2answers
56 views

Darlington Transistors ULN2003APG Base Voltage

I want to control a 30x1 array of pins through a raspberry pi B+. On a breadboard, I set up a series of shift registers (74HC595) to an array of 2V leds, which I can control as intended. After the ...
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1answer
66 views

Reducing transistor switching time with a resistor from base to a negative voltage

Connecting a resistor from the base of a transistor to ground/negative voltage (R in the first scheme below) helps reduce its switching time. I would like to know why and how does it help; what are ...
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2answers
83 views

need help analysing this BJT circuit

I need help analysing this BJT circuit. What I need to find is the equation for IB, IC, and VCE for this circuit. So far what I've got is from KCL : a: I1=Ib+Ic b: Ie=Ib+Ic So I find that I1=Ie, and ...
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1answer
42 views

eliminitaing spikes from the circuit input

Suppose I have a circuit which gets damaged for spikes and high voltages, so that I need to eliminate spikes and high voltages beyond a maximum value, so I have decided for the following two ...
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1answer
185 views

How to sense current with OPAMP?

I want to sense the current that battery supplies to the low current (few mA) circuit. As everyone said before, forcing discrete design does not make sense, so I decided to apply simple OPAMP & ...
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2answers
85 views

faster alternative to 2N3904 [closed]

Can anyone recommend a "general purpose" small-signal BJT NPN transistor that is similar in most regards to 2N3904, but has a higher fT? The 2N3904 has a fT around 300 MHz, but I'd like something in ...
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1answer
61 views

Changing the path of a signal through multiple transistors with a single-poled switch

I was wanting to construct a "fuzz" distortion guitar pedal, but being indecisive, I wanted to be able to change the type of transistors in the circuit at will. I found the idea of using a ...
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1answer
80 views

I need helping understanding this VCO circuit

The two circuits of interest are described in pages 12-14 of Texas Instruments' Application Note 263, Sine Wave Generation Techniques PDF WARNING I'm primarily concerned about the circuit in Fig. 15, ...