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# Active Biasing

40 Threads found on edaboard.com: Active Biasing

## Biasing a Sallen-Key Low-Pass - wording in text not understood

For the benefit of other readers: This problem is as old as audio amplifiers. An active stage, whether a vacuum tube, BJT, JFET, MOSFET or an opamp requires some amount of DC voltage "bias" to operate in class "A"; thus allowing an AC waveform to be amplified. Unfortunately this DC would have a detrimental effect on the previous stage, and thus i

## Transistor biasing problem

Hi I have a transistor that work at active mode . The base input of the transistor is about 0 to 10 volts. The collector is connected to the 24 volts.The emiter output is about 0.5 volts to 9.5 volts. But I want that the emiter output is changing form 0 to 24 volts. The current of this voltage is about 100mA. How can I change my circuit for cha

## "Virtual ground" quarterwave stub for varactor in microstrip VCO.

It appears that one side of the varactor bias is used to bias the active gain device which avoids capacitor blocks thus avoiding additional parasitics.

## How to deal with voltage spikes on secondary synchronous rectifiers?

You shouldn't expect perfect switching from a simple passively steered synchronous rectifier. Forward biasing of substrate diodes and respective reverse recovery can be only avoided with an active control circuit. It's also clear that external schottky diodes will hardly carry the complete load current. If you don't want huge reverse recovery spike

## BJT Biasing Formulas

111307 For this i have have a SOLUTION.But i have a doubt in the solution: Here,base current is found by applying KVL to i/p loop and then Then Ic =βIb and then Ie=gamma Ib=(β+1)Ib So Rc is found by applying KVL to output loop My question is, can we apply formulas like Ic=alpha* Ie(like one,that w

## Howto give differences of Voltages,whenonetransistor is connected in active feedback

Sir, I have used the Avago ATF 54143 transistor to my work and connected the one transistor to other transistor in a feedback mode. How to set the biasing for the two transistors. Feedback transistors how much voltage differences of Vds and Vgs we have to obtain, when we choose Vds= 3V and Ids=60mA.How much voltage differences we have to s

## coarse tuning for LC VCO question

are you designing a microstrip oscillator, or an IC chip? The bigest problem in such things are the parasitic reactances related to the structure. you need some sort of active device (FET or PIN diode) to switch in/out each capacitor, and those devices also require a biasing scheme. All of these things lead to a total reactance vs. frequency tha

## Loop filter issue with practical Amplifier

I indeed found that the PLL loop itself take care of the biasing part. I have a model to analyze the stability, in that model I have tested the 4th order active LF with a VCVS as amplifier. After stabilizing the loop, I put my LF in Transient model and it worked fine. But how to do the stability analysis with practical amplifier ?? As it wont have

## Help with a Noise calculation in a communication channel

Your missing the noise generated by the active devices. For communication equipment it is rare to set impedance by dead weight resistors. Sometimes a resistor may there for biasing, maybe even stability, but is it usually several times higher then the device input impedance to keep the resistor's noise temp from degrading overall noise figure.

## Leakage current in MOSFET

At 90 nm, reverse bulk diode biasing will reduce leakage during standby modes. Obvious other alternative is to power gate circuits not in active clocking. You can also employ dual threshold process option. Low threshold devices for speed, higher threshold for low leakage. You can combine the later two to transfer high speed memory to low leakag

## ny Professional could write equations for IRF510 MOSFET for Id=30mA;Vo=5;Vdd=9?

Dear 10GHZ ( what the high frequency are you !!!!!!!!!:lol:) my mean by linear is active. though , attach your circuit here , please. when you said R1 or R2 or RS , how should i know that what kind of biasing circuit is your mean?!! Respect Goldsmith

## What determinates the CP output voltage for active loop filter

Hello, I'm building a frequency synthesiser using a national semi's PLL. Because, the VCO's tuning voltage is out of the range of PLL power supply. I choose to use a type A active filter as attachment. 52508 I used National semi's easyPLL to get a loop filter with 3order, and test it in real circuit. I found the volta

## Biasing at 0.2mA/um current density

Your bias current changes with the supply voltage, this explains why you see a bigger variation with power supply. You should bias your active device with a current source to keep the bias current constant.

## Transistor for Low Noise Amplifier

I am using ADS2009 may be its version problem uplaod your ADS project so that i can check, design kit is active lib so for S-paramete u need proper biasing circuit. Regards

## dc bias for active capacitance circuit

i am designing an active capacitance circuit for use in a 2nd order LC resonator RF active filter. the software i am using is awr microwave office. my question is, how do i provide dc biasing to this circuit(shown in attachment)? is there an option to directly state Vds and Ids values in the software, or is there a dc bias circuit that will (...)

## Question on biasing basic differential amplifier

For the most basic single ended differential input amplifier with one current source and two active load, both the current source (MOSFET) and active loads (also MOSFET) are required to be biased for expected dc current as I see in text books. Say for example, the current source is to be designed to sink 20uA and the active loads will have (...)

## Pulsed power amplifier - help with biasing TIM8596-15 needed

Hello, can anybody help me? I design pulsed power amplifier and I need help with biasing TIM8596-15. How can I do temperature compensated active gate bias and how can I set right drain current? Pulse width is 300ns-30us, D.C. max 20% and PRF 3-50kHz Thank you

## can any one tell me what is replica baising ?

replica biasing is used in analog circuits where you want exact mirroring of bias currents with currents in active circuits eg. VCO design. Here the acitive part is circuit is replicated in bias circuitry , and same voltages should be maintained to exploit the use of replica bias . please see this , you may get some idea J. Maneatis, “

## Passive biasing vs. active biasing

Im checking out this FET type LNA IC (ATF-54143) that offers two different schemes of implementation (passive biasing and active biasing) What is the difference between the two? Is one scheme better than another in terms of providing gain, rf output?

## source fed mixer problems

What about sweeping the gate bias and plot the drain output.. For best conversion gain an active mixer doesn’t need only proper bias, but also proper matching at RF and LO input and IF output.

## How a self-biasing circuit (latch) is done ?

Hi, In reference to u r ckt, M12 and m13 act as pre charge devices which pull either of out- or out+ to vdd (its explained how this happens in CS amp with diode/active load in razavi) If you use a resistor to do this job, there will b a drop across it so u r output can't reach vdd any time. which is not the case when u use a pmos device.

## using op-amp to provide active biasing for power transistor

Hi, everyone. I have a question about what kind of op-amp I should use to design an active biasing for a power transistor. Basically the I am going to employ a sensing resistor to capture the power supply current from Vcc to transistor. The voltage drop is then compared with a reference voltage by an op-amp. And the op-amp output is connected to

## How do we find out CMOS operation region ?

How do we find out a operation region of a CMOS?. like we say, its operating active region or saturation region?.

## Class AB Power amplifier DC bias

Hi One of the reasons I am interested about this, is regarding active biasing. I have found some articles, that say that active bias can be difficult to achieved with class AB amplifiers. I have attached a paragraph from an article discussing this. I have seen different ways to do active bias. One is where we use a (...)

## What is active biasing in LNA design?

HI, I am interested in a LNA design using BJT for low noise. I am told to use an active biasing to minimise the noise figure and also have a lower VSWR ratio. Does anyone have idea what is active biasing and where can I find information on it? Thanks for the help Rula

## Why do we use replica bias ?

Replicate biasing circuit is a simple straightforward method to ensure that bias current in the active circuit to be biased is exact the refernce current or a fixed ratio to them. The design principle is that the active part of the circuit is duplicated and driven by a reference current. The voltages of the biased devices in the (...)

## PNP and NPN Transistor

the npn vcc is positive also vce to be active if the vbe is -ve then it is cut off in the pnp the opposite is the true

## What is active biasing and where can I find information on it?

HI, I am interested in a LNA design for low noise. I am told to use an active biasing to minimise the noise figure and also have a lower VSWR ratio. Does anyone have idea what is active biasing and where can I find information on it? Thanks for the help Rula

## How is the S11 of an amplifier performed in ADS?

S11 will generally be different between power off and power on. If you want S11 when the amplifier is active, then that's how you should simulate it.

## problems of power combining in PA

Paralleling two or more transistors does not mean "power combining". Power combining consists of "combined powers" that can be delivered from each transistor independently.So, each transistor should have own RF circuitry( they may share biasing circuit with paying attention) and output power must be combined by aid of passive ( or active) combiner

## What are the criteria for designing a biasing circuit?

4th edition of Gray and Meyer teaches you basic to advanced biasing circuits. See active current mirrors chapter. I guess, it is chap.4. Hope this helps.

## Why does unsymmetric signals come out of a symmetric circuit

Your circuit is not symetrical around horisontal axis. Probably biasing points are not well established, or input signal is high enough to make transistors not work in active region.

## What's the bias of BJT/MOSFET?

hi there are many methods to biase a transistor that is to put in the active region to work as a linear device rather than aswitch regards

## How to analyse the role of M55 and M56?

M55 & M56 only carry small amount of current. They are not active transistors, so they don't involve in ac analysis. I guess these two transistors just provide enough biasing current for the M13 & M14 to increase the gm of (M13 & M14). More system information are required (e.g. your circuit application, types of signal your circuit are required to

## filtronic?who could explain resistor ladders in detail???

i found it used for self-biasing at source of fet(filtronic application documents) for designing broadband mpa or lna. the active device is (p)hemt chip. please give some detail information about it,good luck!

## Test Bench for Common Source

Hi! I am new to this forum. My question is, does anyone have an idea of a good test-bench for simulating the Common-Source Amplifier? I mean, how to bias the active transistor(dc voltage at the gate) such that the output is maintained at a particular value, for instance (vdd+vss)/2. The biasing scheme need not be practical. Its just for the sa

## Biasing Small Signal RF amplifier?

Appcad has the capability you need. Go active Circuits, scroll down twice, or more, and you will find the bias calculator you need. g579

## Ideas/design about active biasing for ATF36077

There is an IC from infineon for an active bias circuit. i am not sure that you can use -0.2 v or not.

## Designing the dc biasing circuit of LNA

try active bias circuit, it is more stable voltage for temperature change.

## Can anyone explain passive and active biasing?

active biasing is often used in rf power amplifiers where emitter or source is grounded. Such amplifiers are usually dissipating heat. To improve temperature stability negative dc feedback is used to keep average collector (drain) current constant. Feedback is usually made with PNP transistor.