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# Vco And Amplifier

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30 Threads found on edaboard.com: Vco And Amplifier

## How to calculate ISOLATION VALUE for VCO output?

This post was by mistake posted in wrong forum,I am re-posting it here: I have found out experimentally,I need an isolation of better than 80dB between vco and mixer/modulator to avoid vco frequency pulling to a great extent. Is there a simple mathematical equation to find out before hand the isolation value required ?

## Mixer Design for RF Transmitter

Hi, I am supposed to design a transmitter for my project. I have already pretty much finished the vco and Power amplifier and now need to build the Mixer. My professor said a Passive Quad-FET would be a good architecture to build. But I am confused on how the schematic for this looks. I keep finding different circuits that (...)

## Resistor and capacitor in series

as audioguru said, the purpose of it may vary based on where is implemented (eg. amplifier/DC bias, amplifier matching, vco or others) what type of capacitor it is (tantalum, or ceramic) and configuration (shunt capacitor or series capacitor to ground)

## VCO Frequency sensitivity

Hi all, I have a vco with a sensitivity of 400MHz/V, and my requirement of frequency sweep is 0 to 150 KHz. How can i use the above component, Is it possible to somehow change the sensitivity of the component by adding additional components ? The specification exactly means that by varying the tuning voltag

## Variation in the sensitivity of the receiver with interfacing

Sounds vco Pulling Effect because of Doubler. PLL may not pull-in the carrier in high pulling effects and therefore vco signal can have some ringings about carrier. I guess an isolation amplifier should be used before doubler.

## Fully Differential Op Amp integrator (Cadence)

Hello ,, I am designing an integrator using fully differential amplifier in cadence ....i tried modeling the opamp using vco's ....and it worked as an inverting amplifier ...but when replacing the resistor with a cap ...the cct is not working I need help please

## Placement of decoupling capacitors on PCB trace

for a microwave chip, you want the 100 pf as close as possible, followed by the 100 nf right next to it. The placement of the largest cap is less critical, although if it is a high current device like a transmit amplifier or a low noise device like a vco you would want the big one close by also.

## How can i sum PSD spectrum ?

I think they just add linearly in power. Assuming the two were uncorrelated, if vco had a phase noise of -20 dBc/Hz at 1 KHz offset, and amplifier had -30 dBc/Hz at 1 KHz offset, P = 0.01 + 0.001 = 0.011 which would look like -19.586 dBc/Hz at 1 KHz offset for the series combination of vco and (...)

## Phase noise in vco, mixer and amplifier

Hello! I've plotted vco spectrum in rad^2/Hz. Now i have to apply amplifier noise and mixer noise. I have NF(db) and Gain(dBm) from datasheets. How can i apply it ? Can just summarize as vco+ampNF-Gain etc. ? I am really lost with all these parametrs... any help will be very appreciated.

## Help me improve VCO performance

Hi Guys, I am simulating a vco with the following design: Process: 0.18 um Tool: Cadence Spectre Topology:Three stage Differential amplifier (with symmetric load) Supply: 3.3V Frequency: 2.4GHz I measured the phase noise and it was -100 dbc/Hz at 10 MHz. Is this a good performance? I am using a DC control voltage of about 875 (...)

## Any body know about Low Phase Noise Amplifier???

All passive and active components contribute to the phase noise of the system. If the phase noise of a component is close to the thermal power level, this will be degraded and there is no method to correct the situation. Unlike measuring phase noise in a vco, amplifiers require a much more sensitive measuring system (...)

## Designing a buffer for VCO LC 2.5 Ghz

my vco control voltage get imposition of the oscillation from the output the oscilltaion are of magnitude 32mv i am using accomulation mode varactor the result PLL not getting locked i am using two varactors in series the common point say drain - source are connected to V control thank

## help detune fm radio(88-108mhz) into vhf fm(108 - 175mhz)

One option is to add preamplifier/mixer, based on a dual-gate MOSFET, and a vco .. Depending on the frequency range of the vco, you will be able to receive almost "anything" you like .. Here are examples of pre-amplifier(BF990) and vco(BB149): Regards, IanP

## Ring VCO : Gain of amplifier stages

What happens to the frequency of oscillation of a ring oscillator if I increase the gain of each amplifier stage above the minimum required gain levels? Would the frequency increase or decrease? I would definitely prefer a time-domain explanation.

## Suggest me a VCO buffer design

buffer stage is to convert the output signal from the vco core to a rail-to-rail switching signal . This can be achieved by the use of a two-stage active current mirror makes the input stage, which serves both as a differential to single-ended converter and an amplifier. second stage the inverter is designed to make the output signal ful

## Matching VCO followed by an amplifier stage

Loads change the the frequency of oscillation.Therefore, before optimizing the vco, the real load should be connected and the matching between the vco and buffer amplifier must be fixed and optimized. Otherwise, when you connect your buffer amplifier, the (...)

## Why my PLL unlocks at low temperature?

There are several possible things. For low temperature, the amplifier in the feedback loop misfunctions. Monitor the voltage to the vco control input. Also try characterizing the vco by itself at the low temperature. Measure the frequency for different control voltages at room temperature and at -40. The vibration (...)

## Reciever basic blok question

The mute circuit disables the audio output for situations when a station is not tuned in properly. A frequency locked loop measures the frequency of the vco in some way and adjusts the frequency to be some set value. Another way is to measure the received signal frequency in the IF amplifier stages and adjust the (...)

## How to improve VCO phase noise performance?

Why don't you use emitter follower to buffer your signal?? Or if you tech. is proper source follower ??? Generally we use either emitter follower or Cherry-Hooper limiting amplifier to buffer the vco signals and in measurements we obtain -141dBm/Hz @ 4.6MHz.. Think that...

## Electronic system design

Hello, Does anyone here knows a good site for learning system design? What I mean is, all the books tells you how to design mixers, amplifiers, lna's and vco's, but I never encoutered a site which tells you in the system manner For example, power management - can we share one voltage regulator to amplifier (...)

## PLL IC and 1-16 V tuning VCO

Is it possible to use a PLL IC with 5V power supply with an vco with 1-16V tuning voltage?

## VCO pulling effect and impedance match issues

Hi all, The attached figure is MAXIM2743's(it is a vco buffer amplifier) typical operating circuit from its datasheet, I am very puzzled about it: 1) There is no impedance match between vco output and MAXIM2743 input,it seems that it is in order to suppress vco's pulling effect. So my puzzle is:what is (...)

## How to design a VCO that has a good performance

Hello Redhat, The easy way to design vco is to use your resonant circuits and amplifier at the loop with no real negative impedance amplifier . With elements you can adjust resonant frequency that is shift 0 or 180 degree or what is necessary it depends of amplifier type in feedback loop.The simple (...)

## 90° bend ?? best way to take a feedback from a microstrip ??

hello again... the input is comming from the vco .. 1.3 GHZ then it divided to two parts .. one to RF amplifiers ... two to prescalar as a feed-back the line is a microstrip 50ohm matched.. my questions 1- is it good what i did in the attached image ? if not is there any better suggestions ?

## Differences of Phase noise of VCO and close loop PLL?

Hi, dear Some datasheet: give synthesizer close loop phase noise, e.g. -110dBc at 1MHz, and SpectreRF can measure vco phase noise in open loop condition, my question is: 1. What is diffrence of those two measurements? and how to measurement of Close loop phase noise? 2. Why use close loop phase noise? 3. Relationaship of those (...)

## How to generate sounds electronically?

the answer is not easy...the sn76477 was,in fact,a simple analog synth on a had a vco(voltage controlled oscillator),a noise generator ,envelope generator and vca(voltage controlled amplifier)...all of those blocks can be discretelly built,but it can get really a search in google for modular synthesizer schematics and you'll

## Help building a 915 MHz oscillator and amplifier

Go to this site, ask for a sample, do your design, check the output level and if is necessary put an amplifier. Beware this is a vco and the frequency is not very stable if is not part of a PLL. If you are looking for a stable LO, the cheapest way is to start from a quartz frequency (e.x. 101.6

## The buffer amplifier affects the phase noise of PLL?

Yes... A buffer amplifier will effect the phase noise behaviour of a vco due to changing input impedance of this amplifier concerning of input signal level. What it means ? A signal which is sufficiently high will change the operating point of tha amplifier and this changing will impact the input (...)

## Why we need to add input buffer for RF amplifier?

Buffer amplifiers are used to avoid " frequency offset " phenomena in such a tranceivers. Because , input impedance of an power amplifier is changed by signal amplitude and this may be reason of pulling effect at the output of vco ( or simply oscillator ). When impedance is changed by the signal , oscillator frequency is (...)

## How to modify digital fm receiver frequency range?

This is a question only Philips can answer. Your receiver propably has a phase locked loop and if the vco of the loop can cover the required frequency range they should be able to reprogram the new frequencies. Same thing goes with front RF filters and RF amplifier. If these cover the frequency range fine, if not they might (...)