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# Current Noise Transistor

47 Threads found on edaboard.com: Current Noise Transistor

## [Moved]: noise in high Vth and low Vth FET

Yes, you are right, they should be compared with the same Vov voltage. I just use the same Vgs to bias the high Vth and low Vth transistor, and then observe the thermal noise in the current mirror configuration from them. The thermal noise equation is: in^2=KT*(gm)/3. For the low Vth device has higher Vov, with the same (...)

## Very Low Differential voltage amplification

No real idea for the moment about the voltage or current noise. Perhaps you should review the transistor data of your design kit. You can calculate expectable voltage and current noise for specific transistor size and drain current.

## what's the minimal input current for the Ib current of NPN transisor?

Can the input base current to be as low as 1pA for the npn transistor? Then what's the typical current gain for such low base current? thanks.

## Transistors as diodes

The emitter-base junction of a transistor has a reverse-biased avalanche breakdown at 5V to 7V and is not robust to handle the breakdown current so the transistor will be damaged. Then maybe the base-emitter should be shorted to make a diode.

## calculating resistor to use with transistor pins

Each transistor is manufactured by a few maufacturers and they all publish datasheets that are available on the internet. The datasheets specify the maximum allowed voltage, current and power dissipation. They also list minimum, typical and maximum specifications on things like voltage gain, current gain and noise level. We (...)

## Problem with Inverter

You can also add a snubber circuit near to each switching device. This will reduce the peak current flowing inside during opening period. Another possibility, but it's kind of hard to evaluate without a notion either of the waveform or the board layout, is that the transistor base is receiving induced noise, which could cause undesired (...)

## Amplifier biasing: Methodology?

Hi, I´m working with Virtuoso/Spectre in the design of a low noise amplifier. The very first thing to choose is a proper transistor operating point which provides a good compromise between noise figure (low current) and high gain (high current). I´ve been told that the first thing is to define the (...)

## TIP35C as Pass Transistor Thermal Loss 50%

Linear regulators have low noise but poor efficiency unless Vdrop is held to a minimum. 50% is normal. when input is twice adjusted output. You mention SMPS design but this is not SMPS , which can do 80~90 efficiency. This is a LINEAR regulator. 1st define your acceptable requirements for input and output power, voltage, current

## Relation between Current and Noise (Input or Output referred)

The output thermal current noise increases with the current, but the transistor transconductance also. Then, you calculate the input noise dividing by gm^2, thus the input noise decrases. Consider the MOS thermal noise: SIDout = 8/3 kT gm = 8/3 kT 2ID/(VGS-VTH) and SVin = (...)

## why & how in most of the new applications, FETs are used than BJTs ?

FET is a voltage controlled device and so it doesnt need a high current to drive it where as the power transistor will have very less current gain so its base should be drived with the high current driver, another advantage of FET over BJT is very high input impedance,less thermal dependent noise,etc.., if (...)

## phase noise calculation

hi all, I'm designing a vco with its frquency ranging between 350-550MHz and for doing noise analysis i assume that the maximum phase noise in the circuit will be -120dBc and would like to know how could i find the current required for the shift mentioned above if the width and length of the transistor is known. Please (...)

## Circuit of BC817 as a switching transistor

Most probably your multimreter is drawing a few microamps which causes the leakage current on the amber LEDs Plus noise on the leads. noise (mains hum etc. throug power supply connected to mains ) rectified through LEDs. High impedence voltmeter and small leakage through LEDs makes two resisters in series potential divider circuit

## A problem of my LCVCO phase noise

I have designed a 5GHz LCVCO. when i simulate the phase noise of it, i find the phase noise is bad. Seen from the noise summary, the mainly contribute to the noise is the transistor from bandgap. The bandgap only generate a reference voltage, and convert to bias current for the VCO. When i (...)

## How to design the transistor size in this latch?

Review this book: Model and Design of Bipolar and MOS current-Mode Logic

## Noise or voltage triggered relay

I drew circuit for you, if someone will practice and count component values in circuit. If relay coil current > 100mA , add transistor to drive relay coil. 56089 Regards KAK

## difference between single ended ring and current starved ring oscillator

can anybody tell me difference between single ended cmos ring and differential CMOS ring oscillator?? what is the role of nmos and pmos tail transistor i n current starved ring oscillator?? which one is better between the two? and which one gives better phase noise peformance?

## Help on biasing transistor

the current in MN1 & the resistor R2 will decide the operating point of MN2

## Unwanted spikes on inverting converter output

I haven't found the cause of the unwanted spike: maybe a bad grounding layout, maybe radiated noise from the inductor. I would rather expect the diode reverse recovery behaviour as the main interference source. The commutating current path is usually through output capacitor, output diode, switch transistor and input capacitor. Unsu

## How can I improve the gain of CMOS Gilbert cell mixer?

In CMOS amplifiers reducing current generally improves gain. Perhaps the 2 bottom transistor's should be in Sub-Threshold. This also improves gain. Increase the upper transistor's L (length). This increases channel modulation effect, thus increasing incremental resistance Ro which will increase your gain. If you can't change W/L ratio (...)

## Is noise analysis necessary for all analog IC designs?

noise is quite critical, it depends on the application of your circuits, depends on what you are doing power relates with voltage through current offset can be reduced by larger transistor size, flicker noise is smaller for larger transistor size. noise is not important for some (...)

## How could I create a purely ground for the RF freq?

Hi, currently I am using a large-area SiGe transistor to design a LNA chip, the bias current can be as large as 50mA. The emitter of the transistor is connected to the ground directly to provide a input matching and a good noise figure at the same time. (It is a large-area devices, so it is possible.) (...)

## HELP ABOUT NOISE CALCULATION IN ADS

HI EVERYBODY ADS CAN CALCULATE OUTPUTnoise IN NODES FOR EXAMPLE "Vc.noise" BUT HOW I CAN CALCULATE noise IN current FOR EXAMpLE "Ic.noise" in a transistor collector current instead collector voltage

## Any better alternative to a zener?

I would recommend this. Slightly more elegant than a zener and resistor. Zener wants to be around 9.3 volts. NPN power transistor, heat sink it if you are taking out significant current. If you need low output noise, put a .1 uF in parallel with the zener.

## What is the advantage of using diffusion butting ?

Butting is not recommended in some cases (analog designs), related to the noise injected into the substrate. If the bulk diffusion is close to the source of a transistor carrying a large current, acting as a switch, for example, the noise injected in the substrate is the same amplitude as that source. But if the (...)

## Transistor noise current simulation in spectre/cadence

Do you know how to measure the noise current of a transistor in saturation? I bias the mos in sat region then how to specify/manage the probes in noise analysis.

## Question on circuit to generate power supply noise

You can run BE connection of NPN transistor with inverse current . Amplify signal to desired level and you will have required white noise.

## The size of pmos pass transistor in LDO regulator

Hi, all I am designing a LDO regulator, the minimal power supply voltage is 4.75V, and the output voltage is 4.5V, the maximum output current is 20mA. In order to assure the pmos pass transistor operating in saturation, I have to set a large W/L, but i can not provide this area. My question is that if I choose a smaller size, then the (...)

## Can the LNA iip3 values be positive?

Of course your performance on linearity is better, but in many cases that's not the main spec for LNA's. It is the noise figure you should optimize. It is easy to improve linearity by increasing the current through your transistor, but optimizing for noise involves much more. Unless you're designing an LNA for a Software (...)

## noise in current reference

Hi If the transistor M29( of the fig) is kept in linear region then the noise in the outout current will be very small even at lower frequencies (say 200Hz). Can any one explain the implications if M29 is in triode region?? My bias circuit should give a current reference with the lowest possible (...)

## 2n2222 or Bc109 as switch

The 2N2222 is better as a switch. It has a higher current rating and also, although not be relevant to your application, faster switching times. Don't forget the diode across the relay's coil, or you will fry the transistor. Save the BC109 for that low-noise preamp you will one day build.

## questions about MOS in weak inversion region!

Do you really need to do hand calculation? If hand calculation is not really important to you, how about you try to obtain the desired current straight away from simulation. By biasing it at weak inversion, varies the ration of the transistor. start with single transistor 1st. then you get the rythm when you go for larger circuit. what (...)

## about noise of cascode MOS

hi in general, the noise current contribution from cascode MOS is negligible, but why? i have read Razavi's book but i don't understand yet. somebody can give me an explanation? thanks!

## noise in current mirrors

The noise in current mirrors is mostly bevause of the mirrroing transistor and increases with the factor 'n' by which it is scaled{For eg to achieve a we use W/nL transistor of current Io/n and generate Io current in a W/L transistor ,where noise is (...)

## Can I replace BF197 with BF199 transistor in this VHF amplifier?

Other parameters are: Gain, noise Figure, Linearity, Stability, Supply voltage, current consumption.

## how can I control the flicker noise of bjt

The shot-noise is effectively a limiting floor in LNA design. Unfortunately, it is also a physical limit. The only way to reduce it is to bias the device with a low base current for instance in bipolar transistor. When current noise is a critical point of a design, FET devices are more appropriate! (...)

## How to reduce the collector shot noise in bipolar VCO

the shot noise is mainly depend on the Ic , which is the DC current in collector junction , and if u reduce the IC this will affect the will affect ur gm "the gain of the BJT" wish will affect the oscillation , so u need to be careful when optimize the IC for min shot noise khouly

## noise noise noise ......

iam doing a folded mixer and an amplifier preceding to it. this gain stage is just a differential amplifier with a resistor in place of current bias transistor. (if i use a current bias then noise figure is too big..) I did pnoise analysis(using spectreRF). In the noise report it is (...)

## How do reduce N.F in the LNA design ?

frist of all , u need to bias the transistor to the current which produce the minimum noise then when design the input matching network , then match for minimum noise , get the Ropt , Zopt , and match to it then u garantee that the transistor give minimum noise and u get the (...)

## Simulate the output noise of a single transistor

Hi If You need noise current You should set noise current tab, I think. Then you should disable port noise if you need transistor noise only. Regards

## linearity improvement of a LNA!!

Generally several things can be done 1. Increase the bias current 2. Increase the voltages 3. Use feedback. There are methods using directional couplers that do not increase the noise figure much. 4. Decrease the gain 5. Use a different transistor or if it is integrated, use a longer gate width to increase gm.

## VCO & Output Buffer

The VCO frequency is depended on some parameters such as.. -Resonator components -transistor parasitic elements -Tuning elements such varicaps -Supply voltage -current and Load.. If load is changed, the frequency is also changed. And if that load deviation has very fast changing in time, this will create Phase noise. (...)

## Is power gain S21 or (S21)??

Be aware that there is both voltage and current S parameter. However in Microwave design, we always refer to power S parameter.

## vco phase noise from biasing circuit problem

Hi, I am designing a VCO and find that the phase noise from the biasing circuit contribute almost the same big phase noise. The biasing circuit include some current mirrors to supply the tail current source bias. Anyone has advises to decrease the biasing circuit phase noise? Why reference papers only (...)

## Noise and offset of transistors in weak inversion

Hi, could anyone please provide some materials on dc offset of transistor pair in weak inversion and the thermal noise, 1/f noise of transistors in weak inversion as well? I could only find information on current mismatch of current mirrors in weak inversion from IEEExplorer. Thank you.

## Noise of folded cascode amp.

Dear Rama, I actually think that the reason is that the amount of current carried actually by the cascode transistor is actually lesser than the main transistors. Hence the transconductance is actually lesser. Remember that the thermal noise is actually proportional to gm(input pair)*. Hence the best way is t

## At what frequency should we look for bandgap current noise?

For bandgap at what frequency should we be looking at for output referred current noise? 100kHz? And Why? Thanks

## The function of pass transistor in high current power supply

Pass transistor is usually defined as transistor between Vin and Vout of a linear regulator. For a high current power supply, generally SMPS is applied for high efficiency reason. If so, there will not be pass transistor. However, for some applications in which low noise is a concern, linear regulator (...)