Questions tagged [bipolar]

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bjt reverse active currents

my question is on bipolar junction transistor, npn with 2 emitters, used in ttl nand gate. when in reverse active mode, and 2 emitter are in logic high, how is the collector current calculated ? since ...
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1answer
55 views

How does Bipolar junction transistor amplifies the voltage? [duplicate]

I was looking at Operational amplifier recently, so if you look at the diagram for op-amp, it's just a bunch of npn and pnp junctions. But how could they come together and work as a voltage amplifier ...
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1answer
1k views

Why are circuit results different from theorised?

From the following circuit: I got the following results in comparison to my theorized calculations: Why were my result different to my calculations? Here is my calculations: Equipment used: ...
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0answers
33 views

Calculating Nmax in loaded bipolar junction transistor inverter

I have tried various methods for calculating N max here, and some have resulted in negative answers while others have resulted in an answer of around 1. Is my method correct? Or am I missing ...
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2answers
101 views

Bipolar Transistor Inverter Circuit Analysis

I have been trying to understand this question and I'm just not sure what equation to use for the collector current. I'm not sure if I need to be using an output voltage function of time? All I have ...
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2answers
78 views

PNP Open Collector output series resistor

I have the following circuit to drive a logical output (the input is driven by an MCU): The issue I have is that because of R4, when I want to draw a few mA from the output, the voltage drops. Right ...
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1answer
108 views

Identification of bipolar transistors on die (pnp or npn?)

is it possible to tell from this photograph whether the transistors are npn or pnp? And if so, what is the line of reasoning? How to sort that out? This photo I took is from a Sharp GP1FAV51RK0F ...
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0answers
67 views

Calculating the gain of a specific transistor amplifier circuit

NOTE: There is an error in the drawing above — C1 should be connected to the emitter, not the collector. Hi Electronics SE, hope this is the right place to ask this, if not I'll gladly take it ...
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27 views

isolated and non isolated current and voltage sensing

I am designing Half bridge single phase dual loop(outer voltage and inner current) inverter with 120Khz switching frequency, and i want to sense inductor current and output voltage, conventional LV25-...
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3answers
178 views

Bipolar signal used in differential ADC

I'm trying to find a way to convert a bipolar signal from a load cell (Futek) to an input for a differential ADC on a TIVA microcontroller(TI TM4C123GH6PM). The load cell's amplifier outputs a bipolar ...
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0answers
101 views

Why is a voltage across emitter and base required in a bipolar transistor?

I read the reply to this question but I cannot really make sense of it: In an NPN transistor, why doesn't current flow without applying a base voltage? if I have a npn-transistor and and apply a ...
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2answers
203 views

Why do bipolar electrolytic caps have a long and short lead?

Ok maybe not all, but the Nichicon UES series of bipolar "audio-grade" electrolytic through-hole caps have a short lead and a long lead.. Why? The datasheet has nothing to say about it. This fairly ...
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167 views

Orientation of “bipolar” capacitors on PCB

I've come across a video on a popular and well-respected electronics channel on Youtube where they say that even bipolar capacitors have a preferred orientation in a circuit that minimizes hum and ...
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2answers
118 views

What are the advantages of CMOS operational amplifiers vs bipolar in the same class?

Is there something else than Rail-to-Rail output and possibly lower power consumption for low frequency applications? Or Rail-to-Rail is the main one?
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1answer
35 views

Question about the role of specific element in a circuit (H Bridge)

I am currently studying different ways to design an H - Bridge and came across this circuit. I have a good idea how the bridge works except for the two transistors on the bottom that I have red ...
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0answers
82 views

Amplification equation for AC coupled Common Emitter stages

Do anyone can tell me how to get amplification equation for this circuit of coupled common emitter amplifier? simulate this circuit – Schematic created using CircuitLab Edit 1 Equation for ...
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1answer
76 views

How do I add a bipolar stepper motor to this circuit? [closed]

I have just started electronics at school and cannot find any tutorials on how to do this. I am creating a circuit that when the light intensity increases a bipolar stepper motor will step clockwise ...
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1answer
99 views

H bridge design for bipolar motor

I'm working on a dual H bridge for a bipolar stepper motor. I found these two designs. I would like to know which design would you guys recommend and why? and if there is any component that might be ...
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2answers
102 views

Can I change op-amp supply voltage without affecting circuit behaviour

I am working on an audio project which is based upon various sections of several different schematics from various old musical instruments. I want to make a test board that has multiple different ...
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4answers
366 views

Gain in current but not in voltage -transistor “voltage follower” set up

Suppose we have the circuit set up as shown in the image. Also suppose that $$V_s=\overline{V_s}+v_S$$, where the smal v is for the variable component of the signal which varies much faster than the ...
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0answers
78 views

1.8 V to 5.0 V level shifter with low delay and low rise time

i have a problem with finding the right components and circuit for the following problem. I have a device that is producing trigger signals with a length of 100 ns at a amplitude of 1.8 V (left part ...
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1answer
49 views

Confusion with understanding the fixed bias circuit

Below shows a bipolar transistor in fixed current bias configuration. A text says that this topology is independent of β: What I understand is, since Vcc, Vbe and Rb is constant the base current ...
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1answer
684 views

High voltage linear regulator (with pre-regulator)

I need to build a linear voltage regulator like this: The problem with the usual linear regulators (LM317, LM337, ..) is the limited voltages they can withstand. I have taken inspiration from a ...
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0answers
54 views

Differential Amp - Bipolar transistor

I can't get the same answer as they are getting.. Here is what I'm getting: $$ Acc = \frac{V_{oc}}{v_{ic}} = \frac{-R\beta i_b}{v_{ic}} $$ $$ i_b = \frac{v_{ic}}{r_{\pi+2R_0}} $$ => $$ A_{cc} = \...
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1answer
854 views

Inner structure of a bipolar stepper motor?

The classic diagram looks like this with coils just positioned sideways to the rotation I'm not sure if this is just a schematic or it indicates the actual structure. However I assume the actual ...
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1answer
132 views

Using an NPN tranistor as a switch for two bipolar stepper motors

this is my first electronics project which requires controlling 2 different stepper motors with two motor drivers (L293D). I have found that the number of GPIO pins on my microcontroller (ESP8266) is ...
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2answers
139 views

Doubts on Semiconductor Physics

I'm really confused about the working of a Bipolar Junction Transistor (N-P-N). Just consider the below figure: 1) Clearly the Base-Emitter junction is forward biased and Base-Collector junction is ...
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0answers
139 views

what is normalized transconductance uesd for?

The transconductance is defined e.g. for BJT by gm = dIc/dVBE with VCE=const (1) where Ic is the collector current and VBE is base-emitter voltage, and from (...
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2answers
436 views

Issue with bipolar to unipolar opamp circuit

i want to measure ac voltage.For that i need to shift an ac differential voltage (+1.23/-1.23 across R20) to 0v - 2.5v range for a unipolar adc.The R1,R21,R22 divides the voltage and gives +/-1.23v ...
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3answers
795 views

DC to bipolar DC converters? [closed]

First of all, is there a name for thse kind of converters for easy searching? There are some voltage adjustable DC to +-5-24V DC converters on eBay but they can't handle more than few hundred ...
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2answers
73 views

tri-rail power supply from cheap buck converters

I'm looking to build a 3 rail regulated supply (+5v, +-12v) and I've got a bunch of cheap but functional buck converts from aliexpress. I'm wondering if I can run these off a single AC-DC converter (...
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1answer
96 views

biploar amplifier, voltage gain, and determining resistor values

i've been struggling with this problem. it says that i need to set the resistors of this circuit that produces the highest voltage gain as possible. i got the voltage gain equation, but don't have a ...
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0answers
225 views

PSpice Bipolar Junction Transistors Modeling

i want to simulate the circuit AmpopTBH2, on PSpice. On image 1hbt.png we can see that Draft4 is working fine, on image 2hbt_pardif.png is the same circuit as Draft4 but on PSpice that circuit won't ...
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1answer
118 views

What would happen to the DC bias voltage of the emitter if this capacitor is omitted?

I'm not quite sure what the question means. I need to explain what would happen if I removed the \$1.0 \mu F\$ blocking capacitor from this circuit. Howver, I'm not sure what the "DC bias voltage of ...
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2answers
578 views

Can a 4051 Multiplexer accept +/- 12v bipolar power

I'm looking to use a CD4051B multiplexer as a digitally-controlled switcher for audio signals. The audio is coming from the HP / BP output of a voltage-controlled filter in a synth. The signal ...
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1answer
735 views

Why do we still use Bipolar Transistors for Class A,B Amplifiers?

I'm working on a 4MHz HF power amplifier (Very simple) and was wondering why people still use bipolar transistors for class B amplifiers? Do they have better linear current gain etc. vs a FET? Is it ...
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0answers
577 views

Rin, Rout and Gain of Power Amplifier

I'm trying to find the input resistance, output resistance and gain of this circuit. simulate this circuit – Schematic created using CircuitLab My textbook only has the simpler case when \$R_1 ...
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4answers
802 views

DC Output Voltage of BJT Differential Amplifier with Active Load

I want to compute the value of VO. simulate this circuit – Schematic created using CircuitLab I would have guessed that VO = VCC - VEB. Asuming VCC = 5V and VEB = 0.6 V, that would render VO = ...
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1answer
2k views

Bipolar constant current source circuit

I want to make a constant current source for a few dozen (say 30~60) 2-lead bipolar LEDs by combining a constant-current (CC) source circuit with an H-bridge circuit: simulate this circuit – ...
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4answers
4k views

How does the current travel in Bipolar Junction Transistor (BJT)?

I am completely unable to understand the current direction in npn transistor. in figure 1, the red arrow indicates the electron flow(which is from emitter terminal to collector terminal). thus ...
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3answers
166 views

Bipolar audio amplifier questions

Background: I designed a bipolar audio amplifier to drive a small 0.5W 8 ohm speaker. I am going to use it to listen to other circuits I make. First time doing this since college. Here's the ...
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3answers
381 views

Purpose of series resistors in this bipolar rectifier circuit?

The following circuit uses two series resistors, one for each polarity of the supply. I understand function of smoothing caps and overvoltage zener diodes, but the resistors I do not. I would like to ...
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2answers
318 views

Convert and shift voltage from DAC using opamp

I have a signal coming out of a basic DAC (resistor and capacitor) as follows: 1.4V min 4.8V max ~2.8V pp I have a bipolar supply that is -12V - 0 - +12V What is the best way to shift this signal ...
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1answer
378 views

How did bipolar IC density compare to MOS ICs?

Historically, how did the density of bipolar (e.g. TTL) chips compare with MOS? How complex could bipolar ICs get before they hit limits? Does anyone have a Moore's law-style graph for bipolar ...
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4answers
1k views

Making voltmeter accepting bipolar input voltage, using a microcontroller

I want to build a very simple voltmeter using ATMEGA328 ADC. I can successfully measure up to 20v (using a voltage divider), but the problem is, I don't understand how to measure the voltage properly, ...
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3answers
163 views

Bipolar signal amplifying to high voltage

I have a bipolar (+-15V) square wave with a frequency of approx. 600 kHz. I want to amplify it to +-500V (not precisely), 50W. The load is around 1kOhm. Can anyone give me an advice on how to do it?
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2k views

low power alternatives to LM741? [closed]

I am trying to build a triangle wave generator and the op-amp that kept getting recommended was the LM741. However, according to the datasheet I found, I need to have at least a 10V source to power ...
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2answers
320 views

Modelling transistor V_be and bulk resistance

I'd like to calculate algebraically the DC behaviour of various bipolar transistor circuits that used matched pairs or quads (exponential converters, current mirrors etc.), taking into account the ...
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1answer
204 views

Is it feasible to chain high voltage dc boost converters together to get bipolar (dual) output rails?

I have two Recom R24-150B dc-dc converters (24V in, adjustable up to 220V out) and I want to have +/-220V output rails. The converters need a resistor between the - (COM) output and their adjust port ...
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1answer
69 views

Which are main purposes of bipolar transistors? [closed]

In school, we learned a lot about transistors but I still don't get its point. I understand gain and amplification of voltage or current or both, but I don't get it how can it be used for example as a ...