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3 answers
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Increasing current biases of multistage amplifiers

I remember my professor talking about op amp and he said when we have a multistage amplifier (for instance an op amp) bias current for second stage of amplification must be more than the first stage ...
amin mokarami's user avatar
1 vote
1 answer
81 views

How to confirm PNP transistor is valid?

I am practicing with some basic circuits based on bipolar and MOSFET transistors and have faced with an interesting behavior. I have to extract my PNP transistor from a circuit and have found it ...
Gleichmut's user avatar
  • 131
0 votes
2 answers
62 views

Is it necessary to connect the (-) terminal to earth when connecting two bench top power supplies in series to achieve a bipolar supply?

I have noticed when researching online that it is always mentioned to connect the (-) terminal to earth when connecting two power supplies in series to create a bipolar supply. Is there any issue with ...
Pernel_Sned's user avatar
0 votes
1 answer
52 views

What happens when the CB junction is in forward bias and the BE junction is in reverse bias in an NPN bipolar transistor?

What happens when the CB junction is in forward bias and theBE junction is in reverse bias in an NPN bipolar transistor? I thought of two possibilities: The NPN transistor acts as it is but in ...
Qwe Boss's user avatar
0 votes
3 answers
115 views

+/-10V input voltage to frequency converter

I need to convert a bipolar voltage to a frequency. Say -10 to +10V for the example. For the context this voltage is the error signal from an analog feedback loop. I have a schematics that works well ...
Christian Néel's user avatar
2 votes
0 answers
77 views

How to ramp a bi-polar Return to Zero (RZ) digital waveform

I am using a Raspberry Pi Pico and a few op-amps and resistors to implement an ARINC 429 transmitter. ARINC 429 is a bipolar RZ serial communication protocol commonly used in avionics. See the image ...
ViperJuice's user avatar
1 vote
1 answer
73 views

Diode and bipolar NPN transistors orientation not correct, says JLCPCB

JLCPCB is telling me 4 components are incorrect but when I look over it and the datasheet it all seems correct to me. My original | JLCPCB corrected: This is what my current board looks like: My ...
StealthRT's user avatar
  • 743
0 votes
1 answer
79 views

Need help in identifying SMA package component

I have a problem with identifying a certain element in the SMA housing, which in my opinion has a marking that is inconsistent with what is given in the datasheet (the datasheet which I selected based ...
Karlsson's user avatar
  • 113
3 votes
1 answer
173 views

BJT transistor sum

Here I considered it is in active region and considered Vbe=0.6 V. I did this: I considered it is in active region but it Vce is less than 0.2 V. What should I do next?
Star Lord's user avatar
1 vote
0 answers
120 views

JFET + Bipolar source follower: with VGS constant, how Vout can be an AC signal?

Id is the sum of IB and IR1 with IB small. We can approximatively say Id equals IR1. BJT give an voltage across R1 equals to VBE. VR1 = VBE which is limiting the current flowing across R1. In ...
Acapulco's user avatar
1 vote
3 answers
144 views

Adjustable power resistance

I have to design a circuit that must draw up to 1200 W on 12 VDC to 40 VDC, maximum 50 A, during 100 ms and be adjustable. The first approach was to use power resistors (LTO100) of several values, ...
AdriZ's user avatar
  • 191
3 votes
1 answer
89 views

Is this behavior realistic for bipolar loads on optocoupler outputs?

Background: When using LTspice to simulate such a circuit (the opto-model is called PC357NT and is part of some exhaustive lib called "ZZZ" which I downloaded a long time ago. The PC357NT ...
tobalt's user avatar
  • 22.2k
1 vote
1 answer
281 views

Why is bipolar capacitor labelled with plus and minus?

I need an unpolarised 3300 uF capacitor for an audio amplifier. After googling on the internet, I came to the conclusion that the only way to get such a high value is to use a so-called bi-polar ...
Pygmalion's user avatar
  • 553
0 votes
1 answer
88 views

Using MOSFET to prevent short circuit

I have a circuit where a charger loads a 24 V battery. When the charger is not plugged, there is a risk that of short circuit and the battery will then explode. To avoid this I thought about using ...
cobdmg's user avatar
  • 161
3 votes
0 answers
68 views

Active load and current source purpose on NE5532

I'm trying to do some reverse engineering on the NE5532 schematic, but I can't understand how is designed the current source for the first stage. What I want to analyze now is in yellow on the picture....
tac's user avatar
  • 333
4 votes
0 answers
100 views

Active load role on this circuit and possible uses

simulate this circuit – Schematic created using CircuitLab I came with this circuit to know how an active load can improve it, I still can't finish to understand the role of active loads. The ...
tac's user avatar
  • 333
1 vote
1 answer
141 views

We fabricate P-type and N-type Schottky diodes and a P-type Schottky diode; can a PN-junction diode and PNP BJT be formed?

A Schottky diode is a unipolar device. If a P-type Schottky diode is fabricated on an N-type Schottky diode, can we make a PN-junction diode and a PNP transistor?
Chandra Prakash's user avatar
0 votes
2 answers
195 views

Layperson asking intuitive question about bipolar junction transistor

I am a layperson trying to understand how the bipolar junction transistor works from this excellent article: https://spectrum.ieee.org/transistor-history The relevant paragraphs are as follows: ...
Bob's user avatar
  • 103
0 votes
0 answers
34 views

Bipolar calculations with unkown resistor values and unknown current values

Having a hard time figuring out the current and resistor values across resistor Rf and Rc in an NPN germanium transistor. How do I calulate the current across the collector of the transistor with ...
Heather Cobb's user avatar
0 votes
2 answers
102 views

Is there a problem with my circuit?

The problem is that the curve of the collector's current decreases after reaching a certain (or saturation) point. Should it be this way or there is a problem with LTspice?
levgor's user avatar
  • 1
0 votes
0 answers
54 views

Grounding a bi polar high voltage pulser

This was a "brain teaser" in a circuits class, where only theory is required. Any equations or vocabulary to look into would be greatly appreciated. The question is the following: You are ...
Jinxston Holshue's user avatar
2 votes
1 answer
100 views

ADS1113 ADC saturation at 0 Volts while sampling bipolar signal

I'm using a ADS1113 delta-sigma 16-bit ADC to sample a bipolar signal from a force sensor at 50Hz, and I have found a weird phenomenon. When the signal negative or positive, there is no issue, but ...
June's user avatar
  • 23
0 votes
1 answer
69 views

Creating bi-polar signal from IC's

I'm trying to create a bi-polar square wave from a flip flop but all I get is a positive result. It never goes below GND. I know the second (lower) transistor gets positively biased and maybe this is ...
NaturalDemon's user avatar
4 votes
2 answers
162 views

What does the cross point of V-I curves mean?

Here you see a V-I graph including many curves achieved under different junction temperatures of an IGBT. As it can be seen there is a cross point where all curves intersect each other. Does it make ...
Albert's user avatar
  • 151
4 votes
3 answers
559 views

Pulse oximeter design: How to drive a bi-polar LED having two different forward voltages?

My lab partner and I are building a pulse oximeter for our capstone project and could use some help. I have an ELM-4002 which is a bipolar LED with the following specifications. The two LEDs are ...
Riley Hagerstrom's user avatar
5 votes
1 answer
4k views

BJT vs MOSFET switching speed

I've been reading various answers about the switching speed and frequency of BJTs and MOSFETs, yet I keep finding conflicting answers. Can anyone explain the discrepancy and the real answer? Sources ...
hiitsali's user avatar
0 votes
0 answers
63 views

Is the power consumption of field effect transistors lower than that of bipolar transistors, and why? [duplicate]

Is the power consumption of field effect transistors lower than that of bipolar transistors, and why?
Mathieu Krisztian's user avatar
9 votes
4 answers
1k views

Basic electronics: Transistor switch

I am new to electronics. I am reading this book called Practical Electronics for Inventors. This is a portion about bipolar transistors from the book: There are two things I don't get from this: ...
Dat's user avatar
  • 449
2 votes
3 answers
252 views

Physics of bipolar transistor turn-off

In a class AB follower push pull amplifier output stage* operated open loop and driven from a low impedance source, these are, from top to bottom, the emitter currents of both transistors, their ...
bobflux's user avatar
  • 78.5k
4 votes
1 answer
256 views

Proving that this JFET + Bipolar source follower give back a linear output

I was reading about this source follower and wondered how the bipolar transistor makes Vgs somewhat stable. I believe that what happens here is that when Vin is high more current flows through the ...
PastaLover's user avatar
0 votes
1 answer
57 views

Where can I find the symbolic symbols of various bipolar, JFET, MOSFET in a *unified* style?

Where can I find the symbolic symbols of various bipolar, JFET, MOSFET in a unified style ?
Mathieu Krisztian's user avatar
2 votes
2 answers
732 views

Diode in feedback path of transistor (collector-base)?

This is the schematic for a fuzz circuit. Even knowing that the diode is probably what's providing the signal clipping, I still can't figure out how I'm supposed to analyze the circuit. When V(...
Nick Nagy's user avatar
0 votes
1 answer
85 views

Noise reduction in ECL logic gates

In this ECL circuit, how he got the equivalent circuit for the noise voltage and what is the meaning of hib4 in the equivalent circuit.
Ahmed Redwan's user avatar
0 votes
1 answer
108 views

Qualitative explaination of Output Characteristic of Transistor (BJT) using Depletion layer between Collector and Base

From my understanding, The diffusion layer at a p-n junction is an equilibrium of two opposing forces on charge carriers due to 2 forces - Concentration Gradient and Electric Field caused by Bias and ...
RishiNandha Vanchi's user avatar
0 votes
1 answer
248 views

Parallel Caps as a Bipolar (twin polar in combination)

So, I saw a similar question about 2 caps in series to make a bipolar. Lets assume polar electrolytics I pretty much "get" electronics and build stuff - it works as I expect mostly. I have ...
Michael Nolan's user avatar
4 votes
1 answer
109 views

Generate +/- voltage outputs using two boost converters?

I am working on a project to power some audio equipment that requires +/- 15V DC. Output current load is about 250mA, maximum. I am wondering if there’s any reason I couldn’t create this using two ...
seagull48's user avatar
0 votes
1 answer
66 views

How do I compute the gain on this differential amplifier (in an open loop)?

Hello! I've got this project due for a college course, and the teacher has reviewed my work and said that it is within specification, but he asked me to compute the gain the good old fashioned way ...
Ioan Andrei's user avatar
0 votes
1 answer
749 views

What voltage or node are the BJT substrates connected to in a bipolar process opamp IC?

I've been recently experimenting with converting transistor-level SPICE models of ICs into subcircuits. One thing I try to keep consistent with my subcircuits is that they remain floating; i.e. no ...
Ste Kulov's user avatar
  • 4,543
4 votes
4 answers
853 views

Why are bipolar transistors used for switching applications?

I noticed that many sites targeted at hobbyists recommend bipolar transistors (mostly NPN) to switch things on and off. Bipolar transistors definitely have their purposes especially in analog circuits,...
Karsten's user avatar
  • 439
1 vote
1 answer
205 views

How does bipolar line coding such as AMI work with medium like fiber optics

We know that in bipolar encoding (sometimes called multilevel binary), there are three voltage levels: positive, negative, and zero. The voltage level for one data element is at zero, while the ...
amjad's user avatar
  • 255
0 votes
1 answer
195 views

Why bipolar encoding such as AMI is called bipolar?

In bipolar encoding, we use three levels: positive, zero, and negative. The voltage level for one data element is at zero, while the voltage level for the other element alternates between positive and ...
amjad's user avatar
  • 255
0 votes
1 answer
164 views

Why doesn't this Colpitts oscillator design work?

falstad schematic link My setup: I made many attempts at building a Colpitts oscillator, and this one by far supposed to be the most advanced and with high chance of success. Yet, it's still ...
ScienceDiscoverer's user avatar
1 vote
1 answer
128 views

Bipolar RC Oscillator does not oscillate

Falstad schematic and simulation VCC is 9V. I made hardware version of this first (didn't put too much effort in this simulation) and it's not working. I could read about 3-4 V on CE, so transistor ...
ScienceDiscoverer's user avatar
0 votes
2 answers
295 views

Bipolar capacitor replacement with very different dimension

I need to replace a 25VNP / 10MFD bipolar capacitor (the gray one in the picture). I have a 35VNP / 10MFD (bipolar) capacitor replacement. However it's very small compared to the 25VNP one. The gray ...
elder0010's user avatar
1 vote
1 answer
409 views

BJT reverse active currents

My question is on bipolar junction transistors, NPN with 2 emitters, as used in TTL NAND gates. When in reverse active mode, and when the 2 emitter are logic high, how is the collector current ...
user1781354's user avatar
-1 votes
1 answer
96 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 ...
ShoutOutAndCalculate's user avatar
3 votes
1 answer
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: ...
Redsam121's user avatar
0 votes
0 answers
98 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 ...
Peter's user avatar
  • 33
0 votes
2 answers
2k 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 ...
Peter's user avatar
  • 33
0 votes
2 answers
636 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 ...
Benjamin T's user avatar