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81 Threads found on edaboard.com: Vccs
I need to inject a 20nA sine current through 1 MOhm to 7 MOhm impedance, I made a sine wave oscillator a now I?m trying to do a vccs ckt, I probe two topology appeared in OP-Amp cookbook, but I can?t do a current peak to peak constant varying the load. :cry: Observe that the current is very low and the impedance is very high. Any suggestions
In a macromodel subcircuit, when the normal vccs is used, the accuracy is sufficient. But when the behavior current source is used for the same object, the accuracy is very bad. When the output current is below 1e-9, it will ouput 0. How to solve this problem?
I want to model a two pole amplifier to analysis the settling behavior. At first I tried the transfer function using zero&poles,but the simulation seemed couldn't carry out due to the high pole. Now I'm trying to build the model with R,C,and vccs,but I can't find the vccs model. Any good idea? Regards
Hi all, Any one got experience with vccs or MDB protocol that use in vending machines. I only can find the spec information about the MDB protocol from internet. I am still looking for information about vccs protocol. I wanted to build a device that convert both vccs and MDB protocol to interface with either RS232 or Infrared o
Hello at all, sorry the troubele but I have a problem, i want replace the input trasconductor stage in mixer gilbert cell with two ideal elemnts vccs. I want that this vccs has a gm of 16mS. I attached two schematic, the first is the circuit with input trasconductor with NMOS, the second circuit is with vccs. In the second stage there (...)
Hi All, I am trying to use vccs source in PSPICE with specified transconductance value of 50mS. I am using component 'G' in Pspice for that. The problem is, although i am putting 50mS in value column of 'G', it still simulates the circuit with transconductance =1S. I don't know what is the reason. Am i using the right component? looking forwa
Hi!Did anyone done LDO vccs compensation? I did a LDO vccs compensation, through the voltage-controlled current source to introduce a zero point to elimanate the second main pole. but I have a question, is this vccs output between access R1,R2 will affect the static working point? as shown in Figure 1 NETF points on a current path, (...)
Hi,there! I want to simplify my 5 mosfet amp which is consist of diff. pairs with resistor load.I heard that you can use vccs to replace the input diff. pairs, and the ggain is set to the gm of the input transistor. I know the small signal current can be denoted as i=gm*vgs, then the vccs can model the small signal current cor
I am working on trying to make some impedance measurements and have been reading through a bunch of research papers and everyone seems to be using a Voltage Controlled Current Source(vccs) for their measurements. What I can figure out exactly is why they are doing that as compared to a Voltage Controlled Voltage Source(VCVS). To the best I can tell
refer to "OpAmp cook book" and u will find at least 3 ckts for vccs. BTW I think the current range u need is so small thus requires precision/low noise opamps like OP-07 and even with them u need to use dynamic offset cansellation of the opamp( only for feedback path) or something like that to measure very low voltages. also at this range of cu
Hi, dear friends, Do you know where I can find the vccs circuit? I tried but failed. Many thanks!
for stability test use small signal model which is an integrator (consists of an ideal vccs or CCCS plus one capacitor at output of the controlled source.) if u need more accurate model for transent simulation consiering nonlinear behaveour of pll, make a vco with relaxation oscillator (an ideal schmitt triger plus a capacitor and a voltage cont
the cpld I use is a epm7032slc44, it has 4 vcc's and 4 gnd's. is it necessary to bind them together, or is it enough if I connect just one vcc and one gnd to the supply? thanks in advance martijn
OTA -> Operational Transconductance Amplifier. An OPAMP is Voltage Controlled Voltage Source thus u can not connect output of them together but the output of vccs (Voltage Controled Current Source) can be connected together, cos if the input voltage of any of them is zero, then the output is open circuit. u can use a simple jfet, mosfet or even a
I need to measure impedance (only real part) between 1MOhm to 60MOhm, passing through them a 1khz sine wave, and I can't use more than 20nA pp. I was working in it some time ago, I tested a lot of vccs combinations to sustent this small current. But today I still have troubles to understand or to decide the best way to solve this problem. I need h
You must develop large-signal model and small-signal model first. Usually VCVS,vccs,CCVS&CCCS will be employed to implement.
You can use Voltage Controlled Current Source - vccs, with polynomial coefficients P0=0, P1=0 and P2=1
Hi All, Do you know how to model ideal switch using ideal dependent sources ? :CCCS :VCVS :CCVS :vccs Please help.Thanks.
Hi everyone, I'm doing a course project about sigma-delta macromodel design. According to specs I have to add input-refered-noise to the ideal Gm building block (vccs) in order to calculate the SNR. What confused me is, as the input-refered-noise is frequency-dependent, how can i model it in cadence? What should I add to a vccs? Thank you
hello i need an advice from you. what methods of LDO compensation do you know? simple compensation with output capacitor and its ESR is not enough cause it's susceptible to process and temperature variations. it should add a left-hand zero and no pole into the frequency response. i found only one solution with vccs regards
i tried doing this by changing the vgs of an input transistor and mirroring the current to the inverter stages. but the trouble is that i the current varies non-linearly and by a huge amount for a very small voltage range(of abt 0.2V) and then it moves into triode. so im getting an unreasonable large voltage-to-current gain over a very small input
Dear everybody, I am wondering how I can use "cccs" from analoglib in Cadence to build an ideal differential current amplifier. The cccs is two-port instance, no like vccs and vcvs, which are 4-port instances. Which properties should I specify besides the " current gain"? Many thanks.
That's it, mate .. I just hope that the vccs on both sides aren't of the same source as the whole "optocoupling" isolation wouldn't make sense any more .. Rather name them Vcc1 and Vcc2, or something like that .. Regards, IanP
This slide is from lecture note at UC Berkley. There is error message on Xbalun2 when PSRR's simulating. Isn't the balun bidirectional ? The error message is showed below. "no input to vccs/vcvs at node 0:vo_diff defined in subckt 0" Can somebody help me to solve the problem ? Thanks in advance ! You can see the spice file below. **
This questions is for the SPICE gurus here. I need to model a voltage controlled resistor in SPICE. Its function is similar to that of the VSWITCH SPICE device. For those that are unfamiliar with this device, it attempts to model an almost ideal switch by continuously changing its resistance value based on the controlling voltage. For my pur
why not just using a delay version of vccs which is provided by HSPICE or ELDO. the delay you want is fixed. So you just fill in the delay. You do get frequency dependent phase lag not frequency dependent delay.
Hello all, i am looking for a macro model (using ideal circuit elements such as R's C's vccs..) or a veriloga model. i am looking for one that is fully differential and can model settling and slewing behavior accurately. many thanks
in low frequency small signal analysis we can have a eqivalent circuit which will have a vccs(one for transconductance and the other for body current, RESISTOR). 1. this body current is dominant in NMOS but neglisible in PMOS << rd( see the smaa signal circuit) hence the fina expression depend on 1.type of MO
hi deeptimongia, In the component palette, left hand side drop down list, select Sources-Controlled. vccs is waht you are looking for. good luck,
I will reply how to do in spectre. First, you need to model PFD+CP. You can use vccs source. The gain of PFD+CP is Icp/2/pi Second the VCO is modeled by Kvco/S. You can use a capacitor to model them. Third, you can model divider. It is only a gain with 1/N Fourth, you can model the loop filter using real R and C. Then, you can conne
Hello, renwl The following is my spice deck. *** Balun .subckt balun vd vc vp vn e1 vp vc transformer vd gnd 2 e2 vc vn transformer vd gnd 2 .ends balun *** CKT vx+ vx+ 0 pwl(0 0 1n 0 1.01n 250m 1000n 250m 1000.1n -250m 2000n -250m 2000.1n 250m) vx- vx- 0 pwl(0 0 1n 0 1.01n -250m 1000n -250m 1000.1n 250m 2000n 250m 2000.1n
as b11 is at cons 1V and gm of vccs is 20u its forcing constant current of 20u into the Mos device, as 20u constant current is forced into MOS the voltages are varying accordingly to accomodate the the current and to satisfy the V_I relation of MOS
You can use controlled sources (VCVS, vccs, CCCS, CCVS) to add and invert signals.
hello, i would like to ask one question: We can make ideal opamp in cadence by using VCVS (in analog library)+lpf_1storder(in ahdl library). VCVS set the gain of Opamp, and the lpf_1storder can set the unity gain bandwidth of Opamp. then we can get ideal Opamp to simulate. My question is here: I want to get ideal OTA to simulate OTA-C f
OK, I think that you already have the answer: Because output impedance is high and there is not CMFB, output dc voltage goes near VDD. And, the AC simulation result is wrong. You need CMFB! If you don't have it implemented yet or it is not continuous time, then you need an ideal one. You have to create one block that fixes the
I might misunderstand you, but cannot you just use a current source from your simulator library? Current sinus source? Spice: * Current source: Iname N1 N2 Type Value * vccs (voltage controlled current source): Gname N1 N2 C1 C2 gainvalue Spectre: * pick from a variety of components in analogLib
A bipolar transistor in the active area works rather like a current controlled current source and no way like a linear resistor. Sorry, but that´s not correct. The key parameter for gain calculation is the TRANSCONDUCTANCE (output current-to-input voltage ratio). The BJT is a kind of vccs (because the
Hello guys, I'm trying to model the a generic opamp macromodel and now down to the PSRR stage. Please take a look at the attached picture, I was trying to build a 1st order PSRR model using vccs (G) in the PSPICE, the ouput connected to a small resistor to minic the temperature variation stuff. But this didnt give me useful result. I wonder
hi Old Nick picture (a) is the configuration and picture (b) is the equivalent circuit, the diode is modeled as a current source with its resistance and capacitance, the MOS is modeled as a vccs, my goal is to decide the W/L of the MOS transistor. As you referred, the parameters of reversed-bias diode is varied with different photocurrent, and
The answer is easy. The OTA structure should come close to the ideal OTA as much as possible. That means - high input impedance and high output impedance. As all design formulas and strategies are based on ideal OTA properties (vccs) , all OTA parameters which do not correspond to these assumptions will disturb the filter function. Good (i e. near
if u just want an cursoy model , peak current mode ,u can use vccs to replace the switch mos; voltage mode, u can use vcvs to replace the switch mos. if you want more precision model, u can refer to the book
An OTA when designed using CMOS.... consists of a differential amplifier.... is that wht all an OTA is...??? a differential amplifier with a current mirror?? i realize tht an OTA is a vccs..... does tht mean it works the same way a differential mp works...???
Why do you need to represent an ideal fully differential amplifier with Voltage Controlled Current Sources (vccs)? You can use a Voltage Controlled Voltage Source (VCVS), which is fully differential (in and out). Maybe you need to upload a block diagram of your Multiplying DAC, so that we can understand better what you are trying to do.
Hi, I am looking for CMOS based architectures of the four Controlled sources : * Voltage controlled current sources (vccs) * Current controlled current sources (CCCS) * Voltage controlled Voltage sources (VCVS) * Current controlled voltage sources (CCVS) OTA and CC based one are also welcome Thank you so much for your help. Firas
Atticus: Connect a VCVS (set its gain to 1) at the output of the macromodel you are describing (vccs + R||C) so that it acts as a buffer between this stage and the load introduced by the feedback network of the integrator. This may solve your problem, assuming that you are only checking the frequency response of your circuit in AC simulations.
thank you Keith, yes it helped me a little bit if you can see in slide 10 in the powepoint you posted there is a transistor , and this transistor is a black box. actually to give you an idea, I have simulated a single transistor here is my schematic(single.jpg) and I want to make a circuit with passive components, vccs , etc that gives
Can you try adding the following components to your circuit as shown in the attachment? This will provide CMFB (I hope I didn't mess-up with the polarities). To extract the common-mode voltage you use vcvs and you feed it back to vccs. Let us know the result. Also indicate the ro (rather gds) of the transistors. If you run transient analysis with
my NDR is..... .subckt MolecularDiode pos neg *the vccs model has the problem of staying constant when the voltage is outside the data points Gdiode pos negtest PWL(1) pos + neg 0,0 .08,100e-09 .16,200e-09 .25,300e-09 .32,400e-09 .4,500e-09 .52,600e-09 .55,700e-09 + .65,800e-09 .7,700e-09 .75,200e-09 .78,100e-09 .8
As mentioned by others, negative resistance is essentially a vccs. It commonly comes in the form of cross-coupled circuits. It uses positive feedback and hence often used for hysteresis comparators, latches and oscillators. You may have seen papers where it is used with a diode (ie positive resistor) to achieve a zero small-signal transconducta
... i don't know how to put the vccs . May be this figure can help you? Just specify M ≙ gm , e.g.: vccs:vccs1 node1 node2 node3 node4