275 Threads found on edaboard.com: Variable Capacitor
where can i find these circuits and whats the theory behind them?
the theory behind it is mentioned by Davood Amerion
this concept is mainly used in the ICs or VLSI so that it is not practical to integrate a FM radio in one IC and to connect the IC by a variable cap. at the same size as the hole device :?:. So that we should replace it by a
Electronic Elementary Questions :: 15.01.2006 17:31 :: airman :: Replies: 5 :: Views: 1235
Thank for Hughes's and sengyee88's help.
But except that measure can I implement variable cap. in other easy way?
hspice supports voltage-controlled capacitors. But for spectre, you need veriloga.
Analog IC Design and Layout :: 19.10.2006 19:56 :: Hughes :: Replies: 8 :: Views: 2118
I want to generate a variable capacitor in cadence such as the Cs in figure below.
Cs is changing its capacitive value in a frequncy of 1kHz.
I try making a Cs using VerilogA language. But this can only generate varible current. have found a paper about generate a varable capacitor
Analog Circuit Design :: 23.10.2006 07:47 :: Davidy :: Replies: 2 :: Views: 2937
I would second the idea of a bank of comutated fixed inductors + varicap
But then the question is: what application do you need this variable L and C for?
Analog Circuit Design :: 19.10.2007 02:41 :: kender :: Replies: 7 :: Views: 1691
voltage controlled variable capacitor diodes (VVC)
What is it ?
plz help me.
RF, Microwave, Antennas and Optics :: 09.07.2008 09:20 :: elsalvador :: Replies: 2 :: Views: 1112
I have trouble simulating a variable capacitor that is a function of time, for example C=Co*Cos(w*t). I personally only know this software can allow me to have a time dependent capacitor, but if other softwares are available that can also do the same thing I am more than happy to learn them. But for now, can anyone who has (...)
Software Problems, Hints and Reviews :: 07.01.2010 01:57 :: sl50 :: Replies: 0 :: Views: 1159
I built an oscillator from a design I found in an issue of the ARRL publication, "QST" magazine. I found that the frequency stopped varying when I turned the variable capacitor after a while, although it worked when I first built it. I couldn't find anything wrong with the circuit so, guessing that the trimcap went bad, I soldered in a (...)
Hobby Circuits and Small Projects Problems :: 16.04.2010 21:47 :: obrien135 :: Replies: 2 :: Views: 1358
Im currently designing an RF PA (in the range of 750Mhz, 10W output)
The output matching circuit to the antenna consist of segments of transmission line and variable capacitors (trimmers).
Originally, the PA oscillates, so I try adjusting the trimmers. The thing is, I don't have a plastic screwdriver for adjusting them, so whenever I touch th
RF, Microwave, Antennas and Optics :: 04.05.2010 14:56 :: pepewaw :: Replies: 11 :: Views: 1385
i am unable to use the variable capacitor in my circuits,i.e, which pin of variable capacitor should be connected to which point in circuit?76193
Analog Circuit Design :: 22.06.2012 10:36 :: mk16820 :: Replies: 3 :: Views: 660
I have been trying to make a variable capacitor based off of a lookup table in PSPICE. I found a paper by cadence, A Nonlinear capacitor Model for Use in PSpice, which gives a method of creating a variable capacitor but I am unsure how to actually write the .lib file to implement this design.
Analog Circuit Design :: 27.07.2012 17:44 :: carlmarx :: Replies: 2 :: Views: 572
I need to design a variable capacitor SPICE model. I want to do it with look-up table which would contain a C-V characteristic. Can it be done?
I simulated a IDC with HFSS and now I want to include the results in Spice model. I never used Spice so I do not know how to do it. Can you help me?
Analog Circuit Design :: 10.10.2012 05:23 :: vfurlan :: Replies: 0 :: Views: 370
i want to have a variable capacitor in ads.this capacitor is a model of a mems microphone.please help me
and help me for matching this capacitor with microphone amplifier
thanks for your help
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i want to have a capacitor that variable with voltage and have a flat (...)
RF, Microwave, Antennas and Optics :: 22.10.2012 04:31 :: javad ahmadi :: Replies: 2 :: Views: 185
Check out AN-271 and AN-344 from National, for ideas on how to build digitally-controlled capacitance multipliers.
I cannot find AN-344 any longer on their website, I only have the hard-copy.
Anyway, check out page 5 of the datasheet for this part, that was used in AN-344.
Electronic Elementary Questions :: 17.11.2005 21:03 :: VVV :: Replies: 3 :: Views: 3527
i want to have a capacitor in ADS that its value change with frequency. how can i do this?
RF, Microwave, Antennas and Optics :: 11.01.2008 13:51 :: sedighe :: Replies: 4 :: Views: 1237
How can we design a variable resistor and capacitor in cmos technology.i am talking about resistance of value between 30Mohms upto a 1 Gohm and cpacitance values between some hundred femto farads and few picofarads.
Please suggest possible ways about how this can be done.Any material in this regard would be useful.
Analog Circuit Design :: 27.02.2008 10:55 :: hacksgen :: Replies: 2 :: Views: 1650
I think the pins are O=oscillator, A=antenna and G=ground. They refer to the larger values variable capacitors inside the module. The letter 'F' before them signifies 'FM', a reference to the FM broadcast band. They are lower value variable capacitors on the same shaft.
If you need ones labeled FO and FA, but all you have (...)
Analog Circuit Design :: 21.02.2010 12:00 :: betwixt :: Replies: 13 :: Views: 598
variable capacitor 100 pF have 3 pin, i need datasheet for its and pin configuration?
RF, Microwave, Antennas and Optics :: 29.07.2011 04:06 :: Riski Andami Nafa :: Replies: 1 :: Views: 1229
Here is most commonly used ways to control capacitance value.
variable capacitor - Wikipedia, the free encyclopedia
Varicap - Wikipedia, the free encyclopedia
connecting capacitors in serial or parallel with electronic or mechanical switches
Microcontrollers :: 31.08.2011 01:57 :: kak111 :: Replies: 1 :: Views: 200
That "common" connection in the centre is actually connected to the spindle, so in that circuit, when you touch the knob on the spindle you will be adding extra capacity across the bottom capacitor. Just use one section of the variable capacitor, WITH THE CENTRE CONTACT earthed, and wire a fixed 68Pf in series with it.
Analog Circuit Design :: 22.06.2012 13:11 :: chuckey :: Replies: 5 :: Views: 371
I think it was just to allow flexibility in the wiring layout; in pre-PCB days the wiring was "point-to-point" and a choice of connection point would have been useful since variable capacitors could be mounted in different ways.
Both connection points could be used for different components if the chassis layout made that convenient.
You don't hav
RF, Microwave, Antennas and Optics :: 12.07.2012 21:22 :: krp :: Replies: 3 :: Views: 580
I'm trying to design reader device for RFID applications. But important thing is that frequency will be variable. For this purposes I can use to options: either for different frequencies use separated output stage with chosen value of capacitor or use one output stage and somehow vary capacitance. What is also important: i use microc
RF, Microwave, Antennas and Optics :: 18.01.2013 07:04 :: GeniusRus88 :: Replies: 5 :: Views: 350
Maybe this can give you some ideas :
Hobby Circuits and Small Projects Problems :: 10.04.2013 12:47 :: tpetar :: Replies: 2 :: Views: 354
I have some bad experience with tantalum capacitor (tp)on board after leaving it for about a year or two:
1. While I'm trying to revive an old pc board, two of the tps exploded. I thought something wrong with the board.
2. I'm trying another board, samething happened.
3. While I'm trying to power up my home build variable power supply uni
Professional Hardware and Electronics Design :: 27.02.2002 19:43 :: just_one69 :: Replies: 14 :: Views: 9199
are you using t*s*m*c process?
that's no way to design a "perfect" VCO, but only fit to the specification.
Since the VCO is for 802.11b, should it be 2.45GHz or multiple of it. In this case, you should use LC VCO for its low-phase noise and high prefequency performance.
To start the design, you should have the relevant components,
RF, Microwave, Antennas and Optics :: 28.06.2003 06:07 :: RC13 :: Replies: 1 :: Views: 1243
You can also make your own by putting a variable attenuator in front of a fixed gain amplifier.
RF, Microwave, Antennas and Optics :: 26.09.2003 13:32 :: flatulent :: Replies: 6 :: Views: 1983
- Used together with inductors on LC filters for radio tuning (usually variable capacitors)
- Used as components in oscillators circuits (RC dephasing networks, as load capacitance for crystals, feedback network, relaxation circuits, etc).
- As reservoir for pump charges, to maintain power in backup and low po
Electronic Elementary Questions :: 01.08.2010 10:42 :: zxfeng :: Replies: 15 :: Views: 5444
MOS-FET capacitor is already used in memmory device fabrication. A junction capacitor inside each MOS can be used for storing at least one bit of memmory.
Other applications use MOS-FET capacitor in order to get variable capacitor as varactors, for example, inside the MOS LC oscillator.
Electronic Elementary Questions :: 08.07.2004 23:35 :: mazelk :: Replies: 3 :: Views: 1113
can any body tell me how to tune the rlc (series) and lc (parallel) so that the frequency would be maximum circuit changing the capacitor using variable capacitor?? what do we use, where do we connect it and how?? thanx
RF, Microwave, Antennas and Optics :: 02.02.2005 09:10 :: huji :: Replies: 0 :: Views: 731
2-30p would rather suggest a variable capacitor of 2-30pF. It has 2 pads but on a schematic it may have 3 terminals..
Hobby Circuits and Small Projects Problems :: 28.02.2005 21:44 :: IanP :: Replies: 5 :: Views: 802
I want to generate a frequency variable pulse signal in hspice. For example, the nominal frequency is 50Mhz, at 2us, it jump to 51Mhz, at 4us. it drop to 49Mhz and so on. How to do it? Thanks!
Analog IC Design and Layout :: 17.05.2005 12:20 :: playdc2002 :: Replies: 4 :: Views: 1458
I tried this site and patch it to Proteus. I tried the variable air core inductor and variable capacitor. It doesn't work. Seems only the drawing is given but simulation is not supported.
Can anyone please provide a working simulation for air core variable inductance and variable (...)
Microcontrollers :: 27.08.2005 18:42 :: pete :: Replies: 2 :: Views: 1737
In cadence ic design tool, there is a sample for how to simulate differential LC VCO, it is under dfII/sampls directory. You can read the Spectre RF user guide for more help. For component selection, A-Mode varactor is a good device for variable capacitor, the inductor and active devices are dependent on what frequency your VCO is working on.
Analog IC Design and Layout :: 01.10.2005 02:52 :: pi331133 :: Replies: 8 :: Views: 6359
how could i simulate a variable capacitance whose value could be varied in a specified manner (in spice). i want to run a transient simuation where the capacitance of a cap. would have to vary (this is for an energy harvester ckt.)
Analog Circuit Design :: 09.10.2005 10:18 :: timer :: Replies: 3 :: Views: 724
It's the oldest an simplest radio in MW range. If you add in parallel with the coil, a large (500 pF) variable capacitor, you can even tune it to different stations. It works better in the night. The inductor could be coreless but it need to be around 200 - 300 turns with 30 - 40 mm diameter for the coil shape. Earlier designs, instead of the diod
Electronic Elementary Questions :: 04.11.2005 01:58 :: marie65 :: Replies: 13 :: Views: 1098
Once I built a very similar power supply. You can use the LM350T as a variable regulator. It can regulate from 1.25V to around 30V output voltage.
I would design as follows:
one tranformer with 24Vac x 3A secondary
a rectifier bridge for 50V x 3A (four 1N5404 diodes also do the work)
one 10,000uF x 35V electrolitic capacitor (maybe 4700
Analog Circuit Design :: 14.03.2006 13:43 :: rkodaira :: Replies: 8 :: Views: 7363
Basically I patched two boards according to the provided schematics, one transmitter and one receiver. The variable capacitors for both boards are set at around 10nF so that the resonant frequency is around 120khz. (not exact)
If we assume that original TX oscillator did work reliably :
as schema is with common base based o
Electronic Elementary Questions :: 28.03.2006 10:55 :: artem :: Replies: 10 :: Views: 4672
Except the the circuit board and battery, all parts are from Mouser Electronics. A complete parts list with stock numbers is listed below. The circuit board is available through FAR Circuits. The variable capacitor is available through Electronix Express.
Because this is a superregenerative design, component
RF, Microwave, Antennas and Optics :: 24.04.2006 08:22 :: dunn :: Replies: 3 :: Views: 1000
I've been told an LED diode when it's reverse biased will act as a variable capacitor whose range is dependant on the amount of light falling on the diode junction. Does anyone have an approximate range of capacitance I would expect to find on a generic bright white LED?
Electronic Elementary Questions :: 01.05.2006 01:14 :: Sceadwian :: Replies: 7 :: Views: 1550
trimmer is a kind of variable capacitor
board level designer call small variable capacitor "trimmer" which is often deployed in delicate circuits requiring on production line adjustment.
Delicate analog integrated circuit need on tester adjustments sometimes, like accurate bandgap voltage reference needs some adjustments (...)
Analog IC Design and Layout :: 17.05.2006 01:33 :: jcpu :: Replies: 6 :: Views: 2018
Generally we use a fixed inductor and a variable capacitor in FM tuner circuits.
Hobby Circuits and Small Projects Problems :: 10.09.2006 23:51 :: gunsuresh :: Replies: 1 :: Views: 729
Supercap or ram pages are not required. New external eeproms are cheap and have 64 to 256byte pages. Moving distributed RAM variables to the EEPROM takes a few milliseconds only on a decent 8-bit controller. YOu can easily move dozens of bytes to serial eeprom and give it the 10ms write time and do that with a 1000uf cap as long as you turn off th
Microcontrollers :: 04.02.2007 13:04 :: techie :: Replies: 15 :: Views: 3396
I have a signal of video that have one modulation in FM at 10,7Mhz to send the status of one sensor.
How can eliminate a modulation of 10,7MHz of a signal? It is very important to do it with passive elements. It is possible to make a resonador LC in series to eliminate this frequency?
In order to adjust the resonador, is better to
Analog Circuit Design :: 21.03.2007 08:32 :: kkdelabaca :: Replies: 0 :: Views: 404
In the ancient days a paper tube was used for the coil form. The two coils were wound with close wire spacing. Then as part of the process of tuning in a station the separation between the two coils is adjusted.
The secondary inductance is determined by the variable capacitor capacitance range and the frequency range you want to tune in.
Electronic Elementary Questions :: 02.05.2007 09:58 :: flatulent :: Replies: 18 :: Views: 2061
I've build this oscillator and it works perfect but I need to switch the positions of the 2 variables capacitors to have the 15p-280p grounded (I have some Hf signals coming from antenna) The problem is when I permute the two CVs, I dont have the same frequency range ?? What can I do without changing the circuit? Thanks
RF, Microwave, Antennas and Optics :: 27.05.2007 09:35 :: falcone :: Replies: 3 :: Views: 1731
Try to assign a variable expression instead of the capacitor value
hope it help
Electromagnetic Design and Simulation :: 20.06.2007 18:38 :: grandizer :: Replies: 4 :: Views: 1393
The usual values for L and C are chosen to give acceptable quality factor (low loss) at the working frequency ( series resistance << reactance << isolation resistance). This means reactance between tens of Ω and hundreds of Ω.
If you want to design a radio for brodcasting, you will use a standard variable capacitor, maybe taken
RF, Microwave, Antennas and Optics :: 09.09.2007 07:35 :: Eugen_E :: Replies: 5 :: Views: 689
You need to specify the center frequency. One method is to use variable capacitor diodes and a branch line coupler.
RF, Microwave, Antennas and Optics :: 15.02.2008 11:53 :: flatulent :: Replies: 4 :: Views: 834
I want to build a simple 0-20V variable output DC-DC converter with a max current rating of 1A. It's output voltage will be adjusted according to its output current by using a look-up table.
Since the converter will supply low currents, it'll operate in discountinuous conduction mode.
I have 2 questions:
1 - I don't know how to
Electronic Elementary Questions :: 17.02.2008 08:56 :: s_cihan_tek :: Replies: 4 :: Views: 1132
I have a beginners electronics book and I'm trying to build a time delay circuit out of it to use as a counter. However, I've built the circuit somewhere between 15 and 20 times and I still cannot get it to work. I think maybe something is wrong with it, but I've googled every component thoroughly and feel I have a firm grasp of how it should work,
Analog Circuit Design :: 31.03.2008 19:33 :: laxboy130126 :: Replies: 2 :: Views: 909
Your question is not quite clear.... I assume you want to know what topologies that are usuable for L and C band.
For L you can get away with both lumped (descrete) and distributed (stripline) but at C-band you are better off using stripline type. You can add a multi-turn variable capacitor to tune. A cheaper way would be to add a sma
RF, Microwave, Antennas and Optics :: 15.05.2008 18:05 :: webdog :: Replies: 6 :: Views: 709