Questions tagged [transistors]
The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor), UJT (Unijunction transistor) and MOSFET (FET, for Field Effect Transistor)
5,688
questions
0
votes
0answers
32 views
What is “level of saturation” for transistors?
This is a term I've never heard of, and it's presented on a work analysis of a ttl nor circuit. It basically says that the transistor that links the output with the ground should have a higher "...
1
vote
2answers
41 views
Switch on and off a relay based on two different thermistor values
I am planning to add an electric fan to cool down an old car's radiator based on coolant's temperature.
I have a temperature sensor of which I know the resistance/temperature profile. Let's say when ...
4
votes
5answers
558 views
Difference between no input and a zero input in digital electronics
I'm new to digital electronics and try to understand how logic gates works.
In books many times Zeroes and ones are referred as Low and High respectively, is Low and High used as an indication of ...
0
votes
1answer
52 views
110V Voltage variation with op-amp
I made a project with the objective of changing the supply voltage of a system (VOUT in the circuit) through a PWM signal.
The initial objective was to vary the supply voltage of a secondary circuit (...
0
votes
0answers
26 views
Calculation of V_E of a PNP transistor
In this circuit, I found out the wrong value for V_E.
I calculated I_B with KVL around the 5V source loop and I got I_B = 2.25E-4 A
then I calculate I_E = (beta + 1)*I_B = 9e-3 A and V_E = 10 - 4k * ...
0
votes
1answer
31 views
Unable to control motor voltage with MOSFET and PWM
In an attempt to control the speed of a DC motor with fairly large current draw (up to 1.8 amps) using PWM, I designed the circuit below:
Unfortunately, I am unable to do more than simply turn the ...
0
votes
1answer
49 views
Why place large resistor from gate to ground of MOSFET?
As I was learning about MOSFETS today, I noticed that nearly every circuit diagram with a MOSFET features a large pulldown resistor placed in parallel to the transistor.
For example, in this picture ...
11
votes
5answers
2k views
Why do CMOS NOT gate designs differ from BJT NOT gate designs?
If you look for an inverter circuit on Google Images, you'll find something that looks like this:
This inverter design has a single NPN transistor. However, on Wikipedia's article about transistor ...
4
votes
1answer
111 views
How are the PNP transistors biased in this microphone circuit?
If I am not wrong, the biasing voltage to turn on an NPN transistor is emitter voltage + 0.7 volts.
Similarly, the PNP biasing voltage is emitter voltage - 0.7 volts.
Can someone explain how the two ...
2
votes
2answers
70 views
Which one would be better for 3.3V outputs among ULN2001 and ULN2003?
I intend on driving 24VDC relays with darlington arrays of the ULN200X series. Since the darlingtons will be driven by a 3.3VDC outputs I am hesitating on whether I should choose ULN2003 or ULN2001.
...
2
votes
1answer
54 views
Why does channel length modulation only occur in the saturation region?
As drain voltage is increased, the reverse bias across the drain-body junction also increases and thus the width of the junction should also increase which should deplete the channel length as well. ...
0
votes
0answers
35 views
MOSFET Vds- Vgs graph, looking for intuition on operation regions
I found this Vgs-Vds graph from the this youtube video and I had not seen this kind of graph before for MOSFETS. neither in other sources nor in the few mosfet datasheets I checked out.
It makes sense ...
0
votes
1answer
52 views
Water level sensor giving erratic readings
I am designing a water level sensor using two 2mm graphite rods about 10cm long. I have attached the leads for my schematic to the graphite rods using silver epoxy.
I am using an Arduino Pro Mini pin ...
-1
votes
0answers
52 views
Transistor switching
I have 1 ~ 3 V signal which turns on the LED. I want that signal to act as a switch to drive a relay. I have 12 V power supply in the circuit which could be used to power relay coil. I want to use a ...
0
votes
0answers
38 views
How to calculate I out
All the transistors to operate in saturation region, how should I calculate I-out ? If M1 and M2 are similar than what is the condition to have I out/I REF = 5.
0
votes
0answers
24 views
How to toggle pin between logic low/high and (moderately high) 14V state?
I would like to design a programmer for a 27C512 chip. To erase/program this chip, one needs to put 14V on pin A9. While reading from the chip, either 0 or 5V is put on that same pin.
How to digitally ...
0
votes
0answers
35 views
Get the system to turn on using a voltage source
I am working on a project where i have a momentary push button and i am using this latching circuit to toggle between the two stats, the circuit is working fine.
I need to add a circuit to this one in ...
0
votes
1answer
61 views
Thevenin for BJT base resistors
I want to use Thevenin's theorem with the two resistors connected to the base.
How can I combine those two resistors with Thevenin? Do you have any other better idea to combine them? (circled with red ...
0
votes
2answers
50 views
Naming convention of voltage sources in transistor circuits
Shouldn't the voltage source \$V_{CE}\$, as named by my book's author, be named \$V_{CB}\$ or \$V_{BC}\$ according to the naming convention as this voltage source is between the base-collector diode? ...
0
votes
1answer
73 views
can you please recommend reverse pinout NPN transistor with SOT23 package [closed]
Standard pinouts of transistor looks like this
The Question is I want a NPN transistor with emitter and collector swapped? please share part number you aware of this type.
1
vote
1answer
63 views
Are these scope traces normal for a reverse polarity LED hooked up to an NPN transistor?
I've been trying to make some cheap light sensors using some coloured LEDs and am using the schematic below. The idea is to hook up a bunch of LEDs (Red, Green, Blue etc.) to try and get an idea of ...
0
votes
2answers
90 views
I need advice on a good replacement for a transistor
I have a Pioneer LX-424 receiver. It is the same as the SX-424.
I need to replace transistors, and I need advice about which transistor I can buy.
The receiver has some 2SC1061 transistors.
I don't ...
0
votes
3answers
49 views
Trying to pull a pin on my Gates control board down to GND without a relay
I want to pull my Gates Controller's pin to open the gate down to GND with a esp8266, though I've managed to do this with a relay (shown below)
simulate this circuit – Schematic created using ...
0
votes
0answers
20 views
Sinosuidal inverter,EGS002 Circuit,will it work? [closed]
I made sinusoidal inverter with the EGS002 board but I'm not sure if my design is correct? Or it can be done better.
Anyone can take a look on this?
Datasheet to this board here
1
vote
0answers
69 views
Input and Output Impedance of the Common Emitter Amplifier
I just have solved one of the bjt common emitter question below.
However, I'm curious that how can I additionally find those things below:
1) Input and Output Impedance
2) AC Gain
Here is the example ...
2
votes
1answer
71 views
Is saturation region defined for a “given” collector emitter voltage?
I have seen the traditonal saturation regions graphs (attached). The graph gives the impression that there is a huge region which is saturation region. Shouln't the saturation region be for a "...
0
votes
1answer
28 views
Should I connect the Vout coupling capacitor of a common drain amplifier next to RD or RS?
When designing a common drain amplifier of the circuit linked below, i need to attach a coupling capacitor to the Vout of the circuit. I think a capacitor connected to Vout should be just below RD, is ...
0
votes
1answer
53 views
How does this PNP relay circuit work?
I usually find relay circuits using NPN transistors to drive it on/off. This one has a PNP, will this relay circuit work? What's the difference?
It's a BC858B.
1
vote
1answer
31 views
what units is parameter K measured in, in a MOSFET?
I know how to work out the constant K from the equation:
K = Id / ( Vgs - Vth ) ^ 2
but I can't seem to find what units it is measured in, any help would be appreciated thank you,
I think it might be ...
0
votes
1answer
60 views
Why isn't the emitter current, \$I_E\$, used as the output signal in a transistor?
We know that the emitter current, \$I_E\$, is greater than the collector current, \$I_C\$. So, why isn't the emitter current used as the output signal in transistors for greater amplification?
0
votes
1answer
44 views
Power Calculation of a Buffer with Transistors
I am trying to calculate the power dissipated in my buffer circuit in order to measure the efficiency of the circuit I have built. The circuit can be seen below, and you can also see the DC values of ...
1
vote
1answer
52 views
Analysis of high Frequency Hybrid-pi model of a BJT
Can someone explain the reason behind this modelling of rx?
I had read in the book: "Microelectronics by Sedra & Smith" that rx is added to model the resistance of the silicon material ...
0
votes
1answer
32 views
Resistors for zero crossing detector with optocoupler
I'm trying to understand how to calculate the right value for resistors R1 and R2 in this circuit using the 4N25 optocoupler, and with 12Vac.
With 12Vac, Vp is 16.27v.
In this case, the optocoupler ...
0
votes
3answers
80 views
Does the collector voltage have to be greater than the emitter voltage by few tenths of a volt for an NPN transitor
For an NPN transistor, does the collector voltage have to be greater than the emitter voltage by few tenths of a volt for it to be in active state? If yes what is the reason?
Also it says greater by a ...
-1
votes
1answer
63 views
Can someone help me understand the exact working of this configuration of a Colpitt's oscillator?
So I came across this Collpitt's oscillator in a research paper that I am thinking of implementing but it looks quite different from other configurations and I would really appreciate some help ...
-1
votes
0answers
49 views
AVRDUDE with Arduino won't reset with simple 2N2222 transistor circuit
I'm trying to use a transistor to make a simple reset circuit between a Raspberry Pi (3.3V) and Arduino Micro (5V.)
I'm using the following simple circuit:
2N2222 (base) -> 390 ohm resistor -> ...
0
votes
2answers
52 views
Differential to single ended voltage
I have a question about the stage inside an opamp where the differential input is converted to single ended output.
simulate this circuit – Schematic created using CircuitLab
1)In order for Q3 ...
0
votes
3answers
72 views
Linear voltage regulator dropout voltage
I have a question regarding on linear voltage regulator. The pass element in the linear voltage regulator can be NPN or PNP transistor. If a Darlington pair is used as the pass element, the dropout ...
0
votes
1answer
38 views
Node Technology in Modern Transistors
i was reading about the new 2nm chip IBM created and through some reading i learned that the "nm" part does not refer to the actual gate length like it did many years ago. Can anyone tell me ...
2
votes
1answer
111 views
Audio Amplifier With MOSFET
I am working on a new project that seeks to implement a three-stage audio amplifier. One of my stages consists of a CASCODE circuit using the BF998 NMOS transistor. For this stage I am struggling to ...
0
votes
1answer
59 views
How to control 12 V with Arduino's 5 V pins?
I'm trying to program a parallel EEPROM which requires Vpp high voltage cycle to write a byte. I want to control Vpp with an Arduino pin so I can write a byte onto an address in EEPROM. But I couldn't ...
0
votes
2answers
98 views
Which transistor should be used as a switch for a load of 5 V, 100 mA
I'm new to electronics. I want to use a transistor as a switch for a load of 5 V and around 100 mA.
And what should be the base current or voltage to activate the transistor. Please help me.
3
votes
3answers
245 views
Why does Miller approximation method give the wrong result here?
Does anyone know why using Miller approximation method to calculate the input impedance gives the wrong result here?
The right answer is 1/gm.
I know how to use ...
0
votes
0answers
47 views
Maximum Current Gain Possible for a 100 mA PNP transistor
I have a pulse charging circuit where the maximum current is limited by the hFE of the PNP transistor (DTA144EE). The typical hFE at room temperature is ~220 as shown in the plot below. There is of ...
0
votes
1answer
40 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.
1
vote
1answer
74 views
What the RL as view by this circuit
simulate this circuit – Schematic created using CircuitLab
In this condition, RL=infinity so the voltage gain of the output at the node R5 and Q1 can be obtain as below
$$A_v=\frac{4800}{450}=10....
0
votes
1answer
34 views
I was trying to make this circuit on Proteus but this error appears
I was trying to make this circuit in Proteus as you can see but
"[SPICE] transient GMIN stepping at time=3.12737e-007"
error keeps appearing. How do I make this error go away?
0
votes
1answer
48 views
PNP high-side switching with logic reverse
I am trying to design a High side switch(24V,10A) using a PNP Transistor, the switch control signal is PNP or NPN from the PLC output.
How to select the control signal type (NPN or PNP) using a ...
1
vote
1answer
91 views
Operational Amplifier Output Stage Biasing
I am trying to bias my op-amp output stage using diodes. I am using a current source for the bias current but later I will replace it with BJT current source.
However, it doesn't seem to work. ...
1
vote
0answers
84 views
Why is the emitter resistance not reflected to base?
Considering the first circuit, I want to determine the output resistance seen looking into collector of Q17. When the source \$v_i\$ is zeroed out as shown in the second figure, shouldn't the ...
