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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109 views

Make a zener diode out of a MOSFET

Does anyone know if its possible to wire up a MOSFET transistor as a zener diode? I have been happily making normal diodes from my MOSFETs by shorting the gate and the source simulate this ...
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2answers
39 views

Power Transistor Help

I'm looking to switch an 18v signal at 1 amp with a N-Channel power MOSFET with at least 1.5v to turn it on in a TO-220 package but unfortunately I've only been able to find this one from Fairchild: ...
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1answer
32 views

Replacing a transistor in a CCFL inverter circuit

I have a DC-to-AC inverter circuit that isn't working. It takes 12V DC input and is being used to power a CCFL. The circuit looks remarkably similar to the one labelled "Conventional CCFL inverter" on ...
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3answers
106 views

Transistor saturates no matter the size of base resistor

Problem I have a circuit as depicted below, and after calculating the base resistor, I wanted to see when the base current would be too little to saturate the transistor. I kept increasing the ...
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1answer
41 views

Modeling diode connected transistor in differential amplifier

I have question about the analysis of common-mode gain of BTJ differential amplifier with active load on the Sedra Smith book. In this book, the differential-mode gain \$Ad\$ is derived based on the ...
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1answer
284 views

Very hot mosfet when powering an led strip

I'm basically following this instructable which is using an arduino to control an rgb led strip. I have wired it up exactly as shown, although I didn't use a breadboard i just soldered everything. ...
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2answers
75 views

Parameters for voltage-controlled current source

I'm trying to implement the following circuit in a project: VCC coming in is 18v. The op-amp is supplied with 3.3v. There is a waveform voltage input from 0-2 v that can oscillate at up to 100hz, ...
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2answers
639 views

Why is my transistor ON when charge is only going to the base?

simulate this circuit – Schematic created using CircuitLab I am using an NPN transistor (2N4401). In the above schematic, charge is only coming in through the base, and not the ...
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2answers
92 views

Controlling a Stepper-Motor with 2 H-bridges

I think that I may have come up with a possible way to control a bipolar stepper motor using 2 simple H-bridges. The idea is to control the direction and the steps of the motor by switching the ...
2
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1answer
111 views

How to calculate base resistor of PNP transistor?

I have not worked with transistor much, and therefore need some guidance in deriving the base resistor and pull-up resistor values. I have the following circuit and I want to calculate base resistor ...
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1answer
106 views

Identify surface mount transistor

I could use some help on finding a replacement Transistor. One of the depth finders on our boat has failed and shows a dead short on the power input lines. The problem may be a shorted Transistor in ...
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1answer
78 views

Bipolar junction transistor drawing more than 1 amp

I am trying to use a bipolar junction transistor to sink the current on an output pin: simulate this circuit – Schematic created using CircuitLab But when the base of Q1 is connected to ...
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2answers
74 views

Why one transistor switches on first than other

In the circuit diagram given below we have two transistors. And in the article it is given that one transistor will turn on first. Why this transistor turns on first
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1answer
90 views

BJT instead of FET

I'm making a contact microphone circuit and they say to use a MPF 102 transistor. I was wondering is it ok to use a BJT (that's what I have on hand) instead of the FET. If so would I hook the circuit ...
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1answer
66 views

What is the ideal resistance for a 2N3904 base resistor value when using RTL logic?

I have a ton of 2N3904 transistors and would like to use them for my RTL logic project. Based on what I could figure out on the web, and the parts I had, I've gotten logic gates to work quite well ...
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0answers
39 views

How can I use a 9v chaser board to run LED strips

a few years ago I bought an LED sequencer circuit board kit. Once assembled you can adjust the pace and the brightness with 2 POTs of up to (I think) 8 LEDs. this board runs off of a 9v battery and ...
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3answers
73 views

In a NOT gate circuit, does charge not flow through both the transistor and output line when the transistor is “on”?

I've tried to recreate a circuit from what I think would be a NOT gate, based on some other schematics and breadboard examples that I've seen. simulate this circuit – Schematic created ...
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1answer
79 views

circuit diagram for uninterrupted usage of a 12volt 1amp device using 12 volt 7ah battery with auto charging and full charge cut off

I have a modem which runs at 12Volt 1Ampere , also I have an UPS battery of 12volt 7Ah. I need to design a circuit so that during power outages my modem works from the battery. also a circuit ...
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2answers
62 views

Can we replace the pulse transformer with some other circuit element in this circuit?

Our research group was trying to simulate and analyse this circuit. But it seems that the pulse transformer is creating the problem in the sense that we cannot find its models in Pspice, microcap or ...
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1answer
150 views

Can I use a transistor as a switch to close a pin to GND?

I need to short an external pin to another external pin (gnd). Link to Nikon D90 pinout. I want to control this with an Arduino, can I use a transistor for this? (e.g. BC548)
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3answers
69 views

finding Q point of thyristor drive circuit.

how to find Q point of the transistor shown in the image. the problem is specifically due to pulse transformer.
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2answers
174 views

Transistor Ohms

I've built the circuit in the schematic below to control my TV, the D1 and D2 LEDs are the two mini LEDs from this IR Extender: I've cut it below the female headphone jack and I'm using my ...
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0answers
65 views

Maximum Ohms for IR LED and transistor

I bought a cheap IR extender and I'm trying to use the small sticky cases to control my TV using a Raspberry Pi. The extender has two "heads" with a small IR LED in it and they were connected to the ...
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3answers
91 views

Switch power supply/battery

I have a power supply of 5v DC 5Ah and a 12v 2Ah lead battery. I was thinking to make a circuit to switch battery line when power is off. I made a little schema, what i'd have to put instead of switch ...
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3answers
84 views

Transistor resistance for switching analog signals

I would like to use two transistor to switch on/off two paths to an ADC input so that only one path is active at a time. Is this a bad practice? I'm aware of analog switches but don't know if ...
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4answers
112 views

What are logic gates?

So from what I understand transistors are one of the most important electronic elements for computers because of TTL (Transistors-Transistors Logic). Is this true? If so, how exactly does this work? ...
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3answers
501 views

More Energy Efficient 1 or 0

Is it more energy efficient to have active high or active low pins (I'm thinking shutdown, reset, active type of pins)? Pins that one would not expect to change very often so they will be in one state ...
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11answers
5k views

Why do we need so many transistors?

Transistors serve multiple purposes in an electrical circuit, i.e switches, to amplify electronic signals, allowing you to control current etc... However, I recently read about Moore's law, among ...
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1answer
85 views

Why won't a switching transistor work in this circuit

I've been working with an Arduino lately, and building various breadboard circuits. A simple example was to build a transistor based inverter for a project involving 9600 baud serial combination at ...
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3answers
155 views

What is the best transistor for a large RTL (resistor transistor logic) project?

I've been reading up on older computers like the PDP-1 and TX-0. I'm fascinated with them and love the idea of making a CPU of my own using discrete resistors and transistors. Keep in mind, this is ...
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0answers
38 views

How to test a 3055 with a multimeter?

there have been several good tutorials on this on YouTube. However, I hear about impedances in OHMS. I have measured every possible direction on my 3055 and found 550ohms between emitter and base ...
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1answer
74 views

Need help calculating resistor values for IR LED Driver

I'm wiring an IR LED driver for an Arduino project I'm prototyping. The Arduino will be run at 5V, and I'm planning on using it's 5V output to drive the transistor that runs the LED The circuit I've ...
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3answers
106 views

Transistor working with unusual biasing

What would happen to a BJT if both junctions of the transistor are forward biased? Is there any literature on this? By literature I mean characteristics/equations. Any links would help. I have also ...
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1answer
88 views

Transistor letting 12Volts through collector->emmiter withouit being damaged

I have made a simple digital amplifier using 2N4401 Philips switching transistor. simulate this circuit – Schematic created using CircuitLab I have tested this amplifier on 5 VDC and it ...
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3answers
194 views

Simple low voltage disconnect circuit for Arduino

Preface: Under impression to need a low voltage cut out, to prevent 2x AA NIMH rechargeable battery from being drained too now, and damaging them. (right??) In deployment this circuit will commonly ...
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2answers
128 views

Power transistor or relay?

I'm going to use a microcontroller to switch a vehicle horn on and off intermittently for maybe one second on and one off for a period of 15 seconds; the horn will pull an estimated 3 Amps. I know I ...
0
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2answers
141 views

How to replace this NPN transistor with a MOSFET?

Here is the schematic of the circuit I'm trying to build (source) but I only have an IRF9530N Mosfet; I don't have any NPN transistors at hand. What would the schematic look like with a MOSFET ...
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2answers
60 views

Dynamic Logic - Transistor Sizing

If we have a circuit in dynamic logic: What should the size of the charge transistors (Qe and Qp) be? I know that increasing the size improves the speed but also increases the dissipation, and that ...
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1answer
114 views

Low volume from 1960's radio

I have a 1960's Philips all transistor radio which I restored recently and replaced two of the AF11x PNP germanium transistors on the mixer/oscillator and IF amp stages. After these replacements, the ...
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1answer
51 views

Switching a transistor with audio output

I am wondering how can an audio signal be used to switch a transistor, if the voltage is too low? I am trying to switch some LEDs with the output of an amplifier, but it seems that the audio voltage ...
0
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2answers
124 views

Transistor as switch between similar voltages

I want to use an XBee to relay data coming from a serial device. The XBee will be sleeping most of the time; waking at regular intervals, powering on the serial device, relaying the serial signals, ...
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3answers
168 views

Electronic flasher with low load detection

The circuit above is an existing flasher without low load detection. I am trying to develop electronic 2-wheeler flasher with low load detection. While Googling, I got a circuit with relay in it, ...
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3answers
195 views

How circuit works?

what is the need of Q18 transistor in this circit.
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2answers
78 views

raspberry pi relay

I'm trying to make the Raspberry Pi controlled relay. Searching the internet the whole day, I still cannot get it to work. ( I did not even connect it to the GPIO yet, just using the 3.3v rail). ...
0
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2answers
75 views

How to determine maximum PWM frequency for transistor (2SK2554)

How can I determine (estimate) maximum reasonable PWM frequency for 2SK2554 transistor? I found timings in datasheet: I could estimate frequency from this (and make sure that all these times are ...
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2answers
51 views

K2554 transistor - is it equivalent to 2SK2554?

I have K2554 transistor. There is a symbol similar to Hitachi logo. I can't find datasheet for it. Is it equivalent to 2SK2554? Can I rely on 2SK2554 datasheet?
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2answers
107 views

Avalanche Pulse Generator: Common-collector alike setup with no input and fairly high voltage on the Common

I am wondering what would be purpose of a setup like this? simulate this circuit – Schematic created using CircuitLab If you notice there is no input in this setup and the voltage is ...
0
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1answer
87 views

Two circuits with different voltages - should I use a transistor or an optocoupler as a switch

I am doing a project using the output of a Raspberry Pi GPIO pin (3.3V) to power a 12V remote control. If the two are on different circuits, can I use a transistor to switch on the 12V circuit or do ...
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1answer
68 views

Using Pspice to analyze BJT transistor

As always I have a rookie question. In a project, I need to analyze the circuit below in a way that the transistor would be in forward active mode. I need to calculate resistors and voltage sources, ...
0
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2answers
73 views

Bipolar Junction Transistor Base-Emitter voltage

I've seen several datasheets for Bipolar Junction Transistors providing the value of the Base-Emitter voltage at saturation with values way above 0.6~0.7V (Example). What exactly does this entail? I ...