# bjt

1. ### What is BF in transistor model ?

I simulated ( Multisim ) circuit and checked transistor model I found that in transistors model's description. I noticed BF in description what is it? Is it beta ? If it's same with beta why in model BF is constant when beta not constant? For example : .MODEL 2N2222_Multisim npn +IS=1.87573e-15...
2. ### Switching function of both BJT and Mosfet

Both of this graph show mosfet and but in switching mode As i look at the graph below I notice for mosfet the drain source amplitude is higher than the gate voltage amplitude . However , bjt , collector voltage amplitude is only reach at the same amplitude of base voltage amplitude. From this...
3. ### BJT Multistage Amplifier (Cascaded)

I had been trying to create a BJT Multistage Amplifier circuit which had a total voltage gain of -40. The problem is whenever I tried to calculate the value starting from the total voltage gain it always goes wrong and totally different comparing the simulations and calculations. Anyone can help...
4. ### Operational amplifier MOSFET vs BJT

Hello, I have a question regarding operational amplifiers. Whenever I search for some datasheets of high gain and high-speed Op Amps ( BW higher than 50MHz), I mostly find that they are made of bipolar transistors rather than mosfet. Why is it so? I've done some research and I've found that...
5. ### the first BJT amplifier audio

Hello, I can't seem to find the first all BJT audio amplifier. When and who invented it?
6. ### mesh current analysis in bjt circuits

How to use mesh current analysis instead of thevenin's theorem here to solve for all currents and voltages in the following bjt circuit? How should i make the closed loops in order to analyse?
7. ### NAND gate TTL - How it works

Hello, I am studying digital electronics and I am a bit confused about the saturation conditions of the bjt. I knew that the bjt saturates when the Vce is close to 0 and Vbe >= 0.7. However, when I was reading about TTL I got confused. Can someone give me some intuition and explain me why in the...
8. ### Why did my transistor work?

Hi guys, I designed a simple circuit here to use an Arduino Pro mini controlling a heater rod for my personal project. My heater rod is rated at 24V, 25W. I'm controlling the heater rod using a BJT transistor, FMMT617TA which is some leftover parts from my previous project. After I got my...
9. ### Input & Output Impedances of Common Emitter BJT Amplifier

I want to study about "finding Input & Output Impedances of Common Emitter BJT Amplifier" However, I could not find a decent source & document about it. Could someone supply me with some documents for that. Then that would be gorgeous for my study. Thanks :)
10. ### Input and Output Impedance of the Common Emitter Amplifier

Hi, 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 and my hand draw solution. However, the question only asked to find Vout/Vin... Also, my...
11. ### BJT Common Emitter Large and Small Signal Research

Hi, I want to study about BJT Common Emitter Large (or bias) and Small Amplifier Circuits. My question is I could not find a decent sufficient resource neither from youtube nor from google. :( I want to study about those common emitter large & small signal models, analysis, ac gain, input &...
12. ### The 2N3904 in breadboard test for first time

BJT practice in breadboard Bipolar transistors have three(3) poles, like The 2N3904 NPN Middle pole is base? The left/right poles are chosen arbitrarily,...? If No, how choose the collector? Ground (-) what should be, and what (+)...?
13. ### Why the ratio of Ic/Ib on BJT is not constant?

Hi. The schematic of amplifier using BJT and the result is attached. What I learned is that the beta, ratio of Ic/Ib, would be constant. However, the ratio of Ic/Ib varies by the time. I googled for this and found out that the beta varies with temperature and Ic but does it vary that much...
14. ### Difference between SS8550, S8550 and 8550 BJT transistor

What is the difference between SS8550, S8550 and 8550 BJT transistor? Are they equivalent or not and what does S denote?
15. ### What is Cmeu in an npn BJT operating in saturation mode ?

I know Cmeu is parasitic capacitance in active mode. It's the B-C junction capacitance. But does it change when the npn is operating in saturation mode? Also in general(not just in saturation mode) what happens to Cmeu at increasing Vce? Does it increase? What other things happen to the...
16. ### Do we select a large or small BJT to amplify high frequency response?

Part of me thinks we need a smaller BJT, to reduce base emitter junction area. but I am confused
17. ### NPN BJT Emitter Follower - supply at Collector Current (Ic).?

Greetings everyone, I am planning to design a current amplifier using an NPN BJT Transistor with an Emitter Follower configuration. On top of that, instead of using batteries, I am using 2 separate LDO voltage outputs as the input voltage(Vin/Vbb) to the BJT as well as the supply voltage...