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42 Threads found on edaboard.com: Vga Amplifier
I think it really depends on what your load is. I thought vga was 75 ohms, which is why you need a driver. Not sure why your circuit works at all.
Most of the high-linearity vgas use an integrated step attenuator in front of a fixed gain amplifier, as for example LMH6521 from TI: Advantage using a step attenuator in front of the fixed gain amplifier is not only to keep good linearity, but also to improve input/output match, and the gain flatnes
In the figures it seems to me are showing some simulations, not real device responses. I do not know any real amplifiers having a flat gain from zero to ...9 GHz. Your first vga is not an amplifier but a bare attenuator. Its response can be OK. The second 30-dB amplifier can have the overall frequency response affected by (...)
I think you need to determine what bandwidth you want first. If your vga is -3dB @ 6 GHZ and you need a bandwidth of 50 MHZ, (-3dB) then a 50 MHZ post amp would do. If your post amplifier has also a 6 GHZ -3dB then the final solution would be -6 dB at 6 GHZ. Frank
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I am working on an Analog front End of a receiver, and I find it difficult to know the difference between the variable gain amplifier (vga) and the continuous time linear equalizer (CTLE), can anyone help me with the difference please ?
Apart for selecting a suitable vga, the answer also matters for the ADC and data path design. In so far understanding the datasheet is the obvious first step.
You can use a vga (Variable Controlled amplifier) controlled by an AGC circuit (Automatic Gain Control). If your sync level can be lower than -15dBm, you can use a variable attenuator controlled by an AGC circuit.
please will anybody help me, i want to know how to find the input supply range and output supply range of vga.
I fear, the term voltage controlled amplifier isn't very clear. I presume, you are referring to a variable gain amplifier (vga). It comes in different flavours with rather different specifications regarding bandwidth, linearity and dynamic range. The classical building block for vgas is a gm multiplier respectively a Gilbert (...)
an integrated operationnal amplifier like this one will help a lot... regards, PGA/vga - Programmable Gain amplifier - PGA112 -
See the Hittite vga components: Hittite Microwave Corporation - Products
There are several ways how to control a RF amplifier gain. One is to use a variable (controllable) attenuator with a stable-gain amplifier. Another is to use an integrated vga like RF2637 from RF MicroDevices. There are now many vgas from various IC Manufacturers. Recently, digitally-controlled gain RF (...)
I am trying to simulate agc in matlab simulink. I am unable to find perfect function for variable gain amplifier. i used Vo = k*Vi* exp(a*Vc) where Vi is the input, Vo is agc output and Vc is the error voltage. but this logic dosen't work and my output changes as input changes. Can someone please suggest me a perfect logic for vga in agc. thank yo
There are several IC's called vga (variable gain amplifier) which offer the possibility to control the gain with a dc voltage.
Hi Dear all; I have some questions about RF system design. It is very important. Please help... 1- What is the Input Dynamic Range of a "vga"(Variable gain amplifier)? for example AD8367 2- In a Log Amp Detector if we give a signal larger than it need to saturate the log amp, what happen? Dose the log amp stay in saturation?
Hello everyone, Is there a simple automatic variable gain amplifier that I could use to keep the peak-to-peak output voltage constant at the output of a logarithmic amplifier? I'd imagine I could use the logarithmic amplifier output as a parameter in the error voltage signal. Note that the maximum frequency of the output signal is 50 (...)
What's your input signal? Where does it come from? What are the bounds? Is it an academic class or industrial/research project? Answers to these questions would define the hardware. At the very least you will need a variable gain amplifier (vga) somewhere in your signal conditioning chain. The rudimentary algorithm is pretty simple. - If t
The DC -offset , Actually , this is high pass cirucit, The DC will be remove . Becaue the vga have Band limiter . So that it like bandpass filter.
Applying the offset voltage correction signal to the variable gain amplifier it will adjust the forward gain factor of the vga and the gain factor of the offset loop amplifier. Increasing the forward gains tends to change the cut-off frequencies. Is necessarily to analyze and tune the transfer function of the loop.
Hi,all I am doing a project on designing a variable gain amplifier (vga)under UWB specification. I have conducted several literature research. I found that they included a dc offset cancellation circuit in most of the previous work. And after adding this circuit, the frequency response of the vga will look like a bandpass filter. I (...)
I don't know any part with exactly that specs. Maybe a solution could be the use of an attenuator+vga+PA For example: 10 dB attenuator +10 to -10 dB gain (19 dBm OIP3 at max gain) +20 dB PA (>40 dBm OIP3) Overall: max gain=20 OIP3=38 dBm A starting point could be MAX3538 that has 20 dB control range, max gain 10 dB and output IP3 o
Cannot say the NF measurement is wrong. Can say that is different. For example the high-frequency vga manufacturers usually specify the NF of the controlled amplifier at maximum gain, and sometimes providing graphs for NF vs Gain. Doing an evaluation of the controlled amplifier for NF vs Gain will give an input for your system analysis.
hello,everyone i am doing a vga simulation in cadence, but i come up against difficulties: i want to see the waveform about the gain versus the vctrl(the voltage to control the gain )to certify whether they have exponential relation but i don't know how to do it a reference told that i can ust pss simulation to achieve my aim can anyone told
hello everyone i want to do a vga in uwb system, and in many thesis it should contain a dc offset cancellation cell. In most thesis ,it contain OTA+LPF+(V-I converter) and inserted between the output of the whole vga and the output of the first vga cell it's just a sketch map, and i am not clear how the V-I converter insert in the output (...)
vga=Variable Gain amplifier will fit your requirements with an AGC loop.Otherwise, the amplifier can not understand how much signal has arrived its input and it can not see how much intermodulation will be produced. LNA+AGC system should be considered.
Does anybody know topologies of vga(Variable Gain amplifier) in the literature? Is there any book that explain this or contain important information about the theme? Than you very much for who can help me.
agree with FVM , the vga is a part of AGC loop the AGC loop is a feedback loop , which make the output ampliftude is always constant as the input chanege so it employ a vga khouly
for diode connected load variable gain amplifier band width also varying with gain variation . many receivers architectures use this topology . what is the effect of band width variation on the receiver or any other application?
You can use analog multiplier, but it will be actually regulated attenuator instead of vga. So probably you will have to place an amplifier stage after the analog multiplier.
Hi, AGC is something complex system, the core block is the variable gain amplifier, and the loop is used to detect the output power of the vga and feedback a control signal to the vga to control vga's gain, whose aim is to maintain the output power at a given level. As to the circut, you can search for some papers in IEEE. (...)
"Design of a 1.8 V high frequency CMOS variable gain amplifier with a novel dB-linear gain structure " W Hu, S Song, B Choi, JW Kim, S LSI, S Electron, ? - Circuits and Systems, 2004. MWSCAS'04. The 2004 47th Midwest ?, 2004 - ieeexplore.ieee.org It is kind of you to send it to my email address zhonghan2000@163.com.
If you mean this kind of vga is linear in dB and the outputs controled by the input difference of current, I read some papers about the function of (1+x)/(1-x)=e^2x, sometimes some one will use the current to fulfil this function,for example (I+I1)/(I-I1), the ratio of I1/I is the same meaning of x.
in some power amps or the driver amplifiers , u can change the gain of the amplifier it is vga , and there are now some PA , have two gain modes high gain an low gain so the gain control range as i think is the range u can change the gain of ur PA khouly
I suppose that the vga is operating in the IF domain. There the reduced frequency performance of MOS versus bipolar does not impact the circuit specs. So if you have an vga circuit try to translate them into MOS. Could you make a print of the circuit in mind?
For an IF variable gain amplifier before a 8-bit ADC, what is the noise specification? The output of the vga is constant at 1V peak-to-peak, the channel bandwidth is about 8 MHz (DVB applications). Can I calculate the maximum acceptable output noise density like this: first, for 8bits ADC, SNR should be greater than 50dB, so output SNR of (...)
Hi I have litle exprience: designed cmos gilbert based vga cell Regards
For vga, normally the structures are switched resistance vga on load or source resister chain, switched bias current vga, such as gilbert cell based vga. Also there are some cross couple load structure vga which changes the load by adjust the cross coupled transistor pair. The key point may be how to achieve (...)
Hi~! I would design a vga, which work frequency is about 2GHz. I haven't any experience about this. Can you give me some idea or paper. Thanks very much.
I met with a problem when I was designing the vga with Gain -3 to -21 The Opamp is a 2-stage one with common-source amplifier as the 2nd stage and CMFB. CMFB uses large resistor to sense the output CM. the openloop gain and PM meet my need.and GB is 45MHz. the signal is 200KHz, quite low freqency. I use resistor feedback to generate variable vo
Does some one have recommend for 400MHz IF vga,with analog voltage control and high linearity.dynamic range is 15dB and MAX have >10dBGain,also the price as lower as possible.
Hi. I want design a simple electronic four position vga manual signal switch to feed a vga monitor from 4 (or more) suorces (PCs). Is there someone that can help me? Thanks in advance. ---- EmBlEmA ----