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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Very long transmission-line design tips

I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used: - A DC power supply (24vdc) - B Digital comm - C Ground As ...
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41 views

Basic h-bridge motor driver circuit for audio PWM waves with possible negative voltage

I need to control a DC motor with the PWM audio waves coming out of the audio jack of a device. The device will send a positive PWM to drive the motor forward and a negative PWM signal for driving it ...
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1answer
29 views

Open-circuit Output Voltage of Bipolar Output Stage

In TI's doc Designing With Logic, p. 16, it shows a method to calculate the internal resistance (\$R_{o}\$): using the open-circuit output voltage (\$V_{o}\$) and short-circuit current (\$I_{os}\$). ...
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1answer
34 views

MAx peak to peak of ES without clipping?

This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. ...
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4answers
454 views

Turn a transistor on when any one of nine LEDs is on using an LM3914

I'm wanting to turn a transistor on when any LED from LED2 through LED10 are on with an LM3914 in dot mode. Basically, I want the transistor to be normally off until at least LED2 begins to light ...
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21 views

How to determine resistances to bias BJT based on input impedance, output admittance, and beta of the BJT

I have been given this circuit, with a 2N2222A BJT. I know the input impedance of the BJT is \$ h_{ie} = r_{\pi} = 4k\$, I know the output impedance \$ h_{oe} = 1/r_o = 1/100k = 0.01{\mu}S\$ , and I ...
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1answer
28 views

Why is the signal inverted on a VDB transistor?

I've got a 3904 connected in a voltage divider bias. Probing the input and output I notice that the output signal is inverted. http://imgur.com/PJv0boI Schematic: http://imgur.com/nAIFBW2 Would ...
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4answers
58 views

How to measure DC Operating Point of a simple transistor circuit

Could someone explain to me how to find the DC Operating point of this circuit? I need to find it by running a simulation and probing the circuit, not solving for it mathematically, and I'm not sure ...
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1answer
54 views

Microcontroller circuit

I am using a Stellaris EK-LM4F120XL for a project. The project includes an LCD module, servo motor, ultrasonic ranger and a numpad. The LCD, servo and ranger are rated at 5V operating voltage, and the ...
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1answer
64 views

Make three respective LEDs blink with an LM3914 in dot mode

I'm trying to figure out how to make in the below schematic, LEDs D2, D3, and D4 blink respectively while the LM3914 is in dot mode when their on state occurs. Basically this would act like a warning ...
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38 views

Max peak to peak swing across ES without any clipping distortion?

This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. ...
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2answers
97 views

Low voltage audio amplifier clips on 8 ohm loads

Exposition time: One could call me a freshman in electronics and I just designed my first little audio amplifier for headphones. (Pocket design, I want to be able to drive 4 headphone pairs from a ...
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3answers
810 views

Is this a good way to debounce a switch?

There are plenty of debouncing circuits on the internet, but I couldn't really find one that fitted my needs / available parts, so I came up with my own, from what I had. There's nothing special about ...
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2answers
88 views

Designing a stiff voltage source using an emitter follower

simulate this circuit – Schematic created using CircuitLab I am new to electronics, and I am trying to do Exercise 2.2, page 67 of The Art of Electronics. Use a follower with base ...
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0answers
85 views

I think I have burnt my 24V DC motor

I had a 24V DC motor connected to a Polulu motor driver which was connected to an arduino uno board. I accidentally connected a power supply instead of a volt-meter to both ends of the motor while in ...
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2answers
93 views

An Explanation of CMOS Logic

While trying to understand CMOS Logic on Wikipedia for class, I came upon this paragraph which I can't quite wrap my head around on the duality of CMOS: "An important characteristic of a CMOS ...
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1answer
63 views

Resistance calculation for transistor base

I read this question's answer on calculating the base resistor value for a 2N3904 transistor. I'm in a similar situation however I'm using a TIP3055 to switch a \$V_{CE}\$ of 12V and a \$I_{CE}\$ of ...
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2answers
100 views

How are microscopic transistors on microchips made?

How is something like a microchip which is already small as it is able to house even smaller transistors in the millions at such a micro-scale? It seems like such a feat for machine to be able to make ...
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2answers
117 views

How do you control 130-size DC motors with an Arduino (seemingly 20A DC motors)?

I'm a little confused on specifications and limitations here... I have 3 (130-size, I believe) DC motors I'm attempting to control with an Arduino. They are running off of a 7.2V NiMH battery pack, ...
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3answers
81 views

Need help finding the right transistor for a switching circuit

I have been doing much research to learn about transistors and to find the right resistor/transistor coupling to power a laser driver that I am building. I want to complete the circuit through the ...
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1answer
82 views

Are the stock transistor models in LTspice accurate at RF?

Just checking, I'm doing some experimenting of small signal RF design in LTspice.
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53 views

Commanding numerous motors with one H-Bridge

Is it possible to command more than one motor with an H-bridge like this: Would this work in real life if I replace switches with transistors and command them?
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2answers
557 views

What to do with transistors I had desoldered from TV

I am a beginner in electronic design and want to learn about transistors. I have an old TV and I decided to de-solder the following transistors. Can you tell me what I can use them for, are they ...
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1answer
66 views

Switch Vcc to Ground with a control bit

I have a device that is 1 ohm and it consumes 3Amp. I want to run my device in both ways and I have only one voltage supply. I want to switch ground to Vcc and vice versa with a control bit from mcu. ...
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1answer
51 views

Minimal Hall effect sensor circuit to keep something off after certain RPM achieved

I have a somewhat limited understanding of electronics and circuits. I'm trying to build a circuit that will keep a transistor in an off state after a given threshold of RPM is achieved using a A3144E ...
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2answers
152 views

Microcontroller PWM to bipolar push-pull amplifier issues. (level shifting)

I'm trying to design a circuit that allows a micro controller (arduino) to control a voltage to a load. The load voltage needs to be bipolar in nature (+- 3 to 5 V) for use in controlling a TEC. My ...
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1answer
82 views

Toggle transistors with an shiftregister to light up an LED

First of all I'm quit new to electrical engineering. I had it 3 years in class but I didn't do well. So here is what I plan. I got some shift-registers (74HC595) Which I'll set with an arduino mega ...
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143 views

Integrated LED + Resistor + Transistor

Most designers when are controlling an LED have to make the same old circuit of Vcc -> Resistor -> LED -> Transistor (you need the transistor in case your ...
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1answer
66 views

Transistor: Mix both GND

I Googled a little bit about transistors and I figured out I have a general understanding problem. Can I simply connect the emitter of the transistor to the GND of my microcontroller that controls the ...
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2answers
72 views

Replace mechanical switch with transistor? MOSFET? Relay?

If I have a switch in some consumer electronics that I take apart, and want to replace a mechanical switch with a digitally controlled one, which component should I use? The only problem I see with ...
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1answer
52 views

LV & HV MOSFETs

What are some of the differences between low voltage and high voltage MOSFETs? Obviously the voltage rating would be higher for HV transistors but is there anything that would always be true/false ...
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3answers
157 views

Time constant for RC common emitter circruit

Here is a simple circuit for common emitter. Is the time constant for charging \$C_1\$ equal to \$C_1R_2\$? It doesn't seem logical that \$R_1\$ would influence the charging of \$C_1\$, since it's ...
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1answer
84 views

Switching Between Two Circuit Branches Using Basic Components

I'm working on a project that uses an LDR to switch between two mutually exclusive functions. So, when it's bright and sunny, do X and when it's nighttime do Y. The daytime function will involve a ...
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1answer
45 views

Energy state of transistors

Are there any energy states of transistors? i.e. zero energy, high energy etc. If that is possible, can't we employ the configurations of transistors such as storing memory as energy sources? That ...
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1answer
82 views

MOSFET threshold voltage and body effect

I'm trying to simulate a common drain amplifier on LTSpice which can be used to shift the input voltage either up or down by the threshold voltage (\$V_{IN}+V_{TH}\$ or \$V_{IN}-V_{TH}\$, depending on ...
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3answers
47 views

can SOT883B package BJT transistor switch a relay with 21.1mA coil current?

I am planning to use miniature BJT in a circuit , but I haven't used them before, The specs of NXP BC847BMB TRANS, NPN, 45V, 0.1A, SOT883B shows 100mA as collector current, I am worried if it can ...
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1answer
95 views

Understanding Transistors

I'm relatively new to electronics and I'm trying to understand how to use transistors, but I seem to be misunderstanding something. I'm trying to implement a transistor switch as described in ...
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19 views

Effects of threshold voltage and body effect in PMOS and NMOS devices [duplicate]

Why is it that in PMOS devices limitations due to voltage drop and body effect are not present unlike in NMOS?
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47 views

Transistor CB configuration

I am a beginner in electronics. While studying transistor CB configuration I came across a Question which I am unable to solve. Given is Ic= 4ma and Vcb= 20V To find: Vbe=? Can anyone please help me ...
0
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1answer
66 views

Adjustable charge current from programming resistor for Li-Ion charger - how to change on demand?

I am designing a device which has an integrated Li-Ion battery (single cell, for simple low power portable digital device) and normally charges by way of a buck converter which goes from 12-16V ...
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2answers
59 views

NMOS transistor: how does its structure relate to two interconnecting diode?

There is a popular idea that structure of NMOS transistor could be viewed as the inter-connecting diode across their PN junction. Therefore, when operating NMOS, you always want to keep the Source and ...
2
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2answers
120 views

Capacitor Stacking Charge Pump

I have an infrared LED that needs a voltage drop of ~1.55V as well as a BJT to sink the current when the LED is in operation. That give me a total voltage drop needed of ~2.2V and unfortunately I have ...
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0answers
25 views

Need help finding Vo with changing frequences through the Voltage divider BJT

Help finding Vo with the changing values of frequency. R1 = 11.45k Ohms R2 = 4.4k Ohms Rc = 900 Ohms Re = 324.95K Ohms C1 = 10uF C2 = 10uF C3 = 50uF Vcc = 9V ...
2
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3answers
166 views

Transistors why does increasing base current increase collector current?

I am new to this area so please can you keep your answers simple, thanks. From what I know for an npn transistor in the common-emitter connection the base-emitter junction is in the forward bias and ...
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1answer
34 views

Using a digital signal to turn on and off a vibrating motor

I'm designing a circuit with the IOIO-OTG board and a vibrating motor. The idea would be to have a digital pin on the IOIO board control the state of the motor (either ON or OFF). The motor operates ...
0
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1answer
72 views

How does this PMOS circuit work?

I've been trying to figure out how this PMOS circuit is functioning. B_VCC is 5V coming from a USB port on the board, while VCC5V is used elsewhere in a regulator to create 3.3V but otherwise does ...
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0answers
28 views

Bipolar junction transistor using alternative current amplifier units

Here's the problem: A BJT transconductance amplifier is being convert to a current amplifier And the correct equation for this is: I don't understand how this equation equate to a current ...
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1answer
60 views

Transistor as Switch for 1.5A dc motor

I am using a BD-139 NPN transistor for turning on/off a 1.5A dc motor. the collector current of this transistor is also 1.5A but when I use the transistor as a switch in the circuit only 0.6A passes ...
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2answers
90 views

Most efficient and rigorous way to calculate input/output impedances (transistor circuits)

I've always had troubles with input and output impedances. It is not very well explained anywhere else I could look on the web so... What is the most efficient and rigorous way to calculate input and ...
4
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2answers
149 views

What are the use of these diodes?

I have a circuit diagram which is for a circuit used for testing batteries under a load, only one of the batteries can be tested at a time and I was just wondering what the point of the diodes in the ...