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## Transistor as a switch

A "common base" configuration - adding one resistor and making a divider with about a 1.2V center tap, connected to bjt base, and applying the control voltage (you did not say whether "0" and "1" are voltage, or logic) to the bjt emitter terminal would do what you (say you) want, provided that the control voltage is stiff enough to (...)

## Help with components (pump motor turn on & off)

Could anyone help tell me what type/size components I need with this circuit diagram? 135212135211 I?m going to be using a pump as the motor rated at DC: 3.5-9v 1-3W and my power supply will be DC 8.4V 1.5A. What capacitor, diode, transistor and resistor do I need? Pin 9 will be connected to an Ard

Hi, Have you looked at W. Sansens "Analog Design Essentials"? - Even I can understand CMOS design with this book... Chapter one has some of the formulas for W/L, gM and so on. If that's like a two stage bjt op amp, with no output stage, wouldn't the Vouts end their useful lives at about 600 - 700mV and then hit VDD?

## Temperature Compensation for Ring

Hi, Without knowing anything about your circuit, or the components involved, a simple possibility - if it uses resistors - is to play around with positive and negative tempco values to find a suitable combination that reduces the deviation. This works a bit with bjt circuits to offset the -2mV/?C aspect. Other solutions I've seen involve more co

## Stable bjt voltage drop

Any silicon semiconductor junction forward voltage has a temperature coefficient of about -2 mV/K. Asking for a more stable voltage drop is simply ignoring laws of physics. It makes sense to ask for devices with less type variation of forward voltage, specific leakage or current gain characteristics. But forward voltage temperature coefficient

## Has anyone used BJT in TSMC65nm?

Hello, Has anyone used bjt available in TSMC65? There are pnp and npn transistors in the library and can be used. I wonder if any one has simulated Monte Carlo for those bjt. For MOS, one should replace "_mac" transistor and add "stat_mis" library. How about bjt? there is no "_mac" file to be replaced! Thank you, Vaah

## What determines value of decoupling capacitor e.g when used with mic or bjt stage?

There is confusion about if the capacitor is for decoupling (filtering the power supply voltage) or coupling a signal from the output of one stage to the input of the next stage. The first post says to cancel (block) DC but pass the AC signal and correctly calls it a highpass filter so it is a coupling capacitor. A simple highpass filter has the f

## Troubleshooting problems.

Hello! I'm having a problem answering the following objective questions from my book about troubleshooting bjt amplifiers. For item 19, I answered A and D Assuming the coupling capacitor is open (either the input coupling cap or output coupling cap) the ac output voltage would be zero. But if the bypass capacitor is open the ac output volt

## Basic Concepts about BJT,FET and MOSFET

But in MOSFET the same gain you will get by zero input current.. Both switch and amplifier depends on changing the gate voltage (or base current). Changing gate voltage needs some current because the gate is associated with some capacitance. Power mosfets have significant capacitance and may need considerable cu

## Operational Amplifier types BJT, FET, CMOS

Am I a smartie pants? I recognised the LM741 opamp in your second attachment but I used it only one time and found its performance to be awful. I did not learn about it in school because it was not invented yet.

## Maximum collector-emitter voltage of a transistor in AC regime.

Never came across a bjt with BVCEO of 1.5V. What kind of devices are you asking about? Generally, bjt don't tolerate avalanche breakdown. Pemanent damage can be expected.

## A question about BJT Astable Multivibrators

Hello From: 121517 I read under Title " Astable Operation ": 121509 121510 I could not understand what is underlined. I understand how each transistor turns on but I

## Question about board level connection of a BJT, with external bias current source

Hi, I have one fabricated bjt device (not power bjt) and want to use an external uA current to bias it. However, I have some questions about the board level connecting, and would anybody advise me about the four questions in the picture? Thank you! 120331

## Why npn transistor is not used for high side switching?

Hi, imagine a NPN transistor for the high side switching. In the sipmlest way it is connected to the 5V supply. Now to switch the bjt ON you need a voltage on the base of about 5.6V, But where to get it from, and how to control it? *** With a PNP instead the base voltage needs to be 4.4V instead. So a simple resistor to GND switches the (...)

## Best Books to understand Noise

Hello I have many problems to understand Noise , Noise figure , Shot noise and etc and I have to know completely about calculate Noise to calculate bjt , Mosfet and Block diagram amplifier. I will appreciate that you suggest a good book about Noise with simple steps Thanks

## Proper Relay Module with Proper Isolation

Hi, And about snubber, will just putting on AC side will be enough usually yes. But in detail it depens on many parameters. Like load, PCB layout, sensitivity of the circuit... Klaus

## Best Book To Learn About Transistors (BJTs)

What are the best books or web resources to learn about how transistors (bjts) work, how to analyze them, and how to design using them? Thanks so much!

## question about guard ring vs body effect

Guard ring makes the body resistance where it counts (i.e. right under the channel) lower. The potential of the body relative to source is where the body effect lies. You want no body current, otherwise you have base current in the parasitic bjt and really, really care about body-source resistance then. If there is no body current then you don't

## about hybrid model of bjt

what is base spreading resistance actually in bjt ??

## CMOS dopinf of substrate and nwell

I have designed products in a Nsub, Pwell technology. It was the only one of maybe 20 CMOS flows and subflows in our process portfolio (at the time) that was this way. Construction of this sort gives you a NPN vertical bjt parasitic about the NMOS, rather than a PNP parasitic about the PMOS. Tends to be higher gain (esp. if you do not make (...)

## mosfet driver buffer with jfet

Using a complementary bjt voltage follower raises respectively reduces low and high level by about 0.7 V which involves no problem with standard MOSFETs.

## Delta Vbe current mirror and BJT question

If you mean hanging another base off the {1X, 8X+res} base node, I think the question becomes about the excess base current, where it comes from and what it costs (e.g. more curvature / low temp deflection). Without a schematic to look at I can only speculate broadly. Since references only are used 1X or few-X per chip, is optimizing layout area

## Strange coupling behavior between transistors in ADS simulation

Hi all, I am very curious about a schematic simulation. In ADS 2012, I tried to simulate an S parameter of a single-stage common-emitter amplifier. This amplifier consists of only 1 transistor (bjt). Then, I just added another bjt, which every terminal is connected to ground (let's call this a Dummy bjt). (...)

Relays are quite durable and will last virtually forever if run at their rated voltage so you don't have to worry about it being activated for long periods. I'm afraid that without more information about what the trigger wire connects to, it isn't possible to suggest alternatives but it is quite likely that a better method exists. Brian.

## Can I use a photo transistor to turn on a BJT cleanly?

Aside from the fact that the current directions are all wrong on your diagram, it's impossible to determine what's going on with your circuit. As a rule of thumb, you need to drive the base with about ten times your collector current to ensure the bjt is saturated. A photo transistor would probably be faster.

## Discrete OPAMP Using discrete components (BJT,FET,TUBES) only help

To get a -good- op amp you would have to be pretty selective about components and especially matching. The old timey module op amps did a lot of binning and trimming. You can find many op amp schematics in old National databooks; LM301, LM324, LM741 are about as simple as it gets. And nowhere near "best". A single stage op amp design may be ha

## why the switching speed of BJT is greater than MOSFET?

Very seldom, if ever, true when you're talking about the bjt as a saturating (i.e. any kind of efficient) switch. Raw small signal bandwidth is another matter entirely. bjts have (generally) much smaller Cjc per Ic than a MOSFET has Cdg for Id owing to the construction and physics of the conduction. Just look at the conduction of a (...)

## BJT model parameter extraction

Hello. 1. Can anybody point me papers/books when i can find model's parameter extraction techniques and algorithms for bjt devices (Ebers-Moll, Gummel-Poon, VBIC)? 2. We know about Agilent IC_CAP industry tool for SPICE model parameters extraction. Is the any other tools for this? Does anybody know other instruments for extraction. Maybe anyb

I have been trying to learn about how NPN bjt's work and I cant seam to understand a few things. how to calculate Zi 、 Zo、Av (include Ro) Zi=Rin ~ hFE*(Rb+Re) ( I neglected hFE+1 as insignificant) In 2N2907 graph since Re=0 , Rin reflect the base resistant * current gain product Zo=Rou

## Current variable through potentiometer

I would use a transistor current source. Here's one of about 4,000,000,000,000 pages about it.

## Use of a Base-Emitter resistor in a BJT

Think about Icb0 leakage current and transistor current gain.

## H Bridge driver using discrete components

What is the voltage of your driving signal? If it's only 3V3 you will need logic level mosfets etc. Unless you are running your bridge fast , I would not bother about the difference between 17nS and 11nS. Remember the current into the fet gate is quite short compared to the on time in most cases. bjt's will be easier to build and test with I'd imag

## Logic Level Converter

I have to correct myself. A single bjt can be used if transistor reverse operation is utilized. Reverse current gain is limited to about 1, so the pull-up resistor at the 3.3V bus must not be too low. Instead R1 is supporting the pull-up action.

## 5 MHz BJT COlpitts oscillator using a resonator

How about supplying us with some details of the resonator? Frank

## Help with transistors

Hello, i am new to transistors and i would like to ask a general question about what is actually a transistor, how does it function and what are the general specifications of a transistor. Thank you in advance.

## some question about gate drivers ICs

hi, it may seem naive, but I have some basic question about IGBT/MOSFET dirver ICs. what they do exactly? when I have isolated sources can not we drive the switches using a optocoupler directly? thank you

## dc-ac inverter using astable to drive some 2N3055

...please give me some suggestion about the schematic diagram that i uploaded Inverters based on bjt transistors nowadays is somewhat obsolete. The MOSFET transistors brings better efficiency in terms of energy usage. Another problem on applying 2N3055 is its Beta parameter which may start from 20, requiring 1,5

## MOSFET saturation - voltage drop

Hello, Before posting I have checked several posts but was unable to collect infromation solving my problem. It seems to be simple, sadly it is not

## Commercially available CFA IC in CMOS technology ????

Does anybody knows about any commercially avaliable CFA (current feedback amplifier ) IC in CMOS technology ? The one's I know about are all in bjt or BiCMOS technologies like AD8001 , AD811 , LT1210 etc. Thanks Vipul

## bjt vs mosfet in digital applications

bjts at voltages over about 5V BVceo will be faster than a MOSFET of equal BVdss, provided you stay out of saturation. When I first started designing ICs, early '80s, I was doing single (bipolar) transistor logic, Schottky clamped, and it ran rings around the CMOS of the day (~ 1.5um, 5V). Even today a SiGe HBT that is matched to its CMOS host

## High side switch with bjt

The value of R1 is so low that Q3 will NEVER turn on. R2 provides a current of about 4.1mA but R1 needs about 8mA when Q3 barely begins to turn on. Use 3.3k for R1 then it needs about 0.24mA. Use 3.3k for R1 then the base current in Q3 will be about 5mA and it will turn on properly. The circuit does not need R3 unless (...)

When you want your bjt being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically You misunderstood the point. It's simply about a reversed battery in your simulation circuit. You would connect the co

## BJT question. What is effective collector load?

Hi milan.rajik First of all something about your latest post : I know that for small signal analysis +Vcc is replaced by GND It means you don't know principles of circuit analysis . who told it is replaced by GND ? who told just in small signal ? in fact the DC source is short circuit to the ground instead of AC sources and it is

## Transistor (BJT) bias compensation

Are you asking about maintaining a constant bias point (Ic) across temp, supply? Or are you asking about base current cancellation (compensation)? I think I've seen some reference to it in older analog design texts, back when bipolar devices were still dominant in analog design - Blue-cover Gray & Meyer, etc.) - but a lot of the art was hand-me-d

## Maximum frequency limit of any Power Transistor

I wonder why it's necessary to use 200 or even 500 kHz for LED dimming? Apart form the many right things that have been already said about MOSFET's versus bjt for fast switching, there's another rather simple point. bjt need to be operated with sufficient base current to achieve low saturation voltage. Do you know where you get the base (...)

## Some questions about bipolar junction transistors

Hi. I feel that I have decent knowledge when it comes to mosfets, but there are a lot of thinks I simply don't know about bjt's. With fets I can find Rds(on), Id leakage, gate capacitance and then calculate the time it takes for the fet to turn on and off, but how does this relate to a bjt? What is the turn on-time, leakage current and (...)

## why we don't bias BJT by a battery connected B and E?

I'd like to ask about bjt biasing. Why we don't bias bjt by using a battery connected Band E that has a constant voltage? Vbe = Vbattery = constant and its operating point Q is fixed. 1.) The value of Vbe that is necessary for a particular Ic value is not known with sufficient accuracy because of very large tol

## Modulating Ic on a BJT

It's better to tell the basic specifications and the intended purpose of the circuit rather making us guess about reasonable parameters.

## Modulating Ic on a BJT?

Some parameters don't fit at all, causing failure of the overall circuit. You e.g. have a 100 A current source in the photovoltaic element model but an output resistance that doesn't allow more than mA. The bjt might sink 1 or 2 A according to base current limitation, etc. Instead of making us guess about reasonable parameters, you should bett

## BJT vs MOSFET DC-DC SMPS Circuit

Hello, I have been trying to make DC-DC Buck Converter but now actually after knowing more about its complications, i would like to know how to get maximum switching frequency of any Bipolar Transistor or MOSFET ? Because in datasheet its maximum switching frequency is not written. What is Transition Frequency given in the datasheet ? Can i u

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