Questions tagged [bjt]
BJT stands for Bipolar Junction Transistor. It is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications.
2,806 questions
3
votes
4
answers
258
views
Zener+Capacitor+BJT-based noise generator: How to calculate the DC bias on the output by hand?
I am exploring the DC values on a noise generator given by the Circuit Digest web page at Simple White Noise Generator Circuit. Expressed in CircuitLab, we have:
simulate this circuit – ...
- 269
4
votes
2
answers
284
views
Query about circuits containing BJT and Zener Diode
I have a question about the following image (question number 35 on page 10 of the GATE 2011 EE question paper):
I am not asking for your help to solve this question. I already have an answer key as ...
- 100
4
votes
3
answers
656
views
Why is a DC bias voltage (V_BB) needed in a BJT amplifier, and how does the coupling capacitor make this possible?
Source: "Electronic Devices", Floyd, 10th Edition, Fig. 4-21, p. 180
I’m learning about transistor amplifiers and I want to make sure I properly understand the role of the bias voltage and ...
- 59
2
votes
2
answers
305
views
Boost converter transistor voltage weird behavior
When designing a boost converter where the BJT is powered by a square wave from a relaxation oscillator (using TL071CP), I get a weird voltage signal when measuring Vce of the BJT MPS2222A. It appears ...
- 539
0
votes
0
answers
69
views
Measuring BJT Gummel Characteristics with Keysight B1500A: Do I Need Three SMUs?
I want to measure the Gummel Plot of a bipolar junction transistor (BJT) using a Keysight B1500A. My setup includes two medium-power SMUs (MP-SMU) and one GNDU. The connections are: emitter → GNDU, ...
- 11
0
votes
3
answers
162
views
How is a BJT a current source?
I have always had this confusion, and I'm finally ready to ask it, after reading the answer here: https://electronics.stackexchange.com/q/755447
There are many questions here that seem tangential to ...
- 185
6
votes
7
answers
873
views
Voltage across Vce in a common emitter BJT
As the base current increases collector current increase. This causes the voltage drop across the collector resistor to increase. That makes real good sense, but I do not understand that why always ...
- 2,045
-1
votes
1
answer
84
views
Optocoupler saturation
IC MPN- FODM2701R2
I am giving If=5 mA current through diode.
CTR is 300%.
Ic current through transistor will be 15 mA.
R1=0 Ω.
R3=1500 Ω.
Therefore I am limiting the max Ic current to 3.33 mA.
...
- 1
2
votes
2
answers
223
views
Crystal quartz oscillator is it good for amplitude modulation?
I am in need of a sine wave generator for a AM modulator I am building.The carrier signal of my AM modulator will be at 10MHz.I searched through the internet and found a circuit on https://www....
- 512
2
votes
4
answers
80
views
Why does a decrease in collector current result in an increase of collector voltage (making \$V_c\$ more negative)?
I have read Navy's textbook Module 7 - Introduction to Solid-State Devices and Power Supplies and it says:
"When a (PNP) transistor is connected in a common-emitter configuration, the input ...
- 21
1
vote
1
answer
69
views
Interchanging/swapped Emitter and Collector of a NPN BJT - detection by measuring its diodes, but why BC diode has lower voltage
Measurements with Swapped Emitter and Collector
I wanted to measure 6 pieces of a BC547C (npn BJT) Q1...6 that each drives a relay (24 V, 75% on, 2.88 kOhm) powered by an old notebook SMPS of 19.5 V ...
- 370
1
vote
2
answers
163
views
How to lower distortion in common base configuration?
I'm trying to make an amplifier with a common base input followed by an emitter follower, and I'm getting outrageous distortion figures when I simulate it in Multisim. For example, for a 5 mV (10 mV p-...
- 29
0
votes
0
answers
89
views
Relationship between Early effect and some small-signal four-pole BJT parameters
The Early effect (caused by base width modulation) is a well-known effect in transistor physics.
In the classical four-quadrant set of characteristic BJT functions, the Early effect affects the ...
- 29.5k
2
votes
1
answer
139
views
How is the voltage calculated in this current mirror implementation?
I've seen this kind of implementation of a double bjt current mirror (Pull-Push current mirror?) in the 7805 Voltage regulator. I´m trying to understand the way it works by making a simple model on ...
- 23
2
votes
2
answers
222
views
Why are low frequencies being amplified more than high frequencies by the BJT in this amplifier?
I've been trying to make some simple amplifier circuits, but I realize now that there is a big piece of the puzzle that I'm missing. I have a simple bandpass filter feeding into the amplifier, but ...
