Questions tagged [vco]

VCO (Voltage-Controlled Oscillator) is an electronic oscillator whose oscillation frequency is controlled by a voltage input.

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33 views

PLL for Audio Frequency VCO using R divider

I'm attempting to design a PLL for an analog, audio frequency VCO, but I've run into a conceptual problem. I can't reasonably use a divider in the feedback path. My reference frequency would ...
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1answer
58 views

Fractional Frequency Divider

let's consider a fractional frequency divider, which is defined (wikipedia) in the following way: A fractional-n frequency synthesizer can be constructed using two integer dividers, a divide-by-n ...
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2answers
44 views

Phase Comparator and VCO in PLL

I have a basic question about the simplest PLL scheme: The purpose of this scheme is that of generating a signal which is a perfect copy of the input signal (which comes for instance from a crystal ...
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1answer
35 views

VCXO Control Range Above 0V

So I think this this going to be a simple answer but I just cant really find anythign that confirms this for me. This is the VCXO in question: Q-Tech QTCV356 The control voltage range is 0.3V min, ...
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1answer
46 views

Strange powering of the TL710 comparator

I have an old schematics of 80th fancy synthesizer VCO. It uses the TL710 comparator, that according to the datasheet has -7V Negative Supply Voltage. I cant find the emitter-base breakdown voltage ...
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30 views

How can I test wether my OCXO VCO is working fine?

I recently bought a PTOC32227 OCXO (datasheet) from eBay (secondhand). It is supposed to output a square wave at 10MHz. However, it is a part of a bigger circuit that is not working properly and it ...
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4answers
74 views

What does D2 do in this schematic?

Can somebody clarify what the purpose of D2 is in this schematic: I understand that we are taking a clock input from the Sync jack to the transistor. The reset pin (4) is pulled high to Vcc, until ...
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387 views

Finding Equivalent Transistors (BC178 and 2N2646)

I have an old schematic which uses two obsolete transistors, the BC178 and the 2N2646. By searching I was able to find that the BC178 can be replaced by the BC177 as written on this page: http://www....
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3answers
92 views

VCO Input Capacitance

I'm trying to figure out the input capacitance of a VCO I am looking to use. The datasheet of the device does not specify an input capacitance. However, it does include the following. illustration ...
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2answers
110 views

VCO SN74LS624 - understanding pin out / how to read datasheet?

I have a SN74LS624 chip and I am trying to get it working on a simple breadboard with an oscilloscope. I have read the datasheet here: http://www.ti.com/lit/ds/symlink/sn54ls629.pdf I can not ...
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950 views

Does this VCO produce a sine wave or square wave

I'm looking at the datasheet for the analog devices hmc431lp4 voltage controlled oscillator, and I can't tell if its output waveform is a sine wave or square wave. The datasheet doesn't label the ...
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1answer
145 views

Trouble with FSK VCO modulation circuit

Circuit shown is a VCO that reliably creates a 200MHz sine wave at 3V pk-pk. I would like to use this VCO to create an FSK modulated signal. My bit 1 frequency = 200Mhz and my bit 0 frequency = 205Mhz ...
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1answer
191 views

Analog exponential convert for MFOS VCO

I'm trying to understand the exponential converter in the MFOS VCO. Here is a link to the complete MFOS Noise Box synth schematic. http://musicfromouterspace.com/analogsynth_new/NOISETOASTER/...
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2answers
137 views

Capacitance divider of Colpitts Oscillator

For the following Colpitts Oscillator, Why does employing the capacitance divider up-converts the source impedance of transistor by a factor of (1+C2/C1)2
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3answers
154 views

VCO circuit Analysis

can you help me with the basic comprehension of this Voltage Controlled Oscillator scheme (it was used in a PLL)? I do not understand why there are two varactors instead of one, and the role of the ...
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1answer
63 views

Generating fixed count pulse train from single pulse

EE novice here. I have an analog synth oscillator core which produces a sync pulse each time the waveform resets. I'd like to generate a short series of pulses triggered from each sync pulse, ideally ...
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1answer
139 views

Two details about phase noise have been confusing me for a long time. Hope to be resolved

Just like FLOYD M. GARDNER said in the PhaseLock Techniques, 3rd Edition: "In light of that success in spectrum analyzers, a practitioner’s answer to the question above is: The spectrum of phase noise ...
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2answers
741 views

Grounding Vcc and Vee?

I recently started electronics as my hobby. I'm working on this v/oct modular synth and in the schematic that I was working on, it did not make sence to me when all the Vcc and Vee are connected to ...
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2answers
362 views

Can Zener or Schottky diodes be used as a substitute for varicap diodes in tuning a VCO?

In particular, this would be a fairly low frequency VCO with a frequency range of 10 Hz to 20 kHz. I'm thinking of the configuration with the T-junction that has 2 opposite facing, reversed biased ...
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28 views

BLE VCO Function Divide by 2

Can someone explain or point to some documentation that explains how the RF front-end works for BLE chips? Specifically, I am confused about why the VCO runs at 4.8Ghz and is then divided by 2. I have ...
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1answer
247 views

Link between phase noise and linewidth for a oscillator?

I was googling for a formula to transform the dbc/Hz value given in data sheets for VNA, spectrum analyzers and VCO is often given in dBc/Hz with offset. Now looking up research papers about future ...
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1answer
59 views

Is it possible to power down all the PLLs and VCO of a MAX 10 Device?

We are developing a board in which we would like not to use the analog features, like PLL, VCO and ADCs of a MAX10. UG-M10CLKPLL par. 2.3.6 states : "The only time that the VCO is completely disabled ...
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1k views

Using ICL8038 as a VCO

I wanted to use this function generator IC as a voltage controlled frequency output especially to obtain low frequency sine waves. But unlike many implementations, I wanted to control the frequency ...
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1answer
162 views

Horn antenna for radar sensor

I have InnoSenT SMR-314 and SMR-334 radar sensors that have quite wide horizontal radiation pattern of over 100 degrees (see datasheet on page 3). I would like to make the sensors far more directional ...
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123 views

Finding the Analog Bandwidth of a Voltage Controlled Oscillator

We've built a current starved voltage controlled oscillator And tuned it so it works only in the linear region, which means it oscillations between 720-840 mV, and outputs 3.6-4.4 GHz. In order to ...
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5answers
274 views

Is there such a thing as a resistance oscillator?

I think I understand how a Oscillator works (VCO). One uses an Oscillator when one wants for example a square wave oscillating between sy, \$0\$ volts and \$5\$ volts. My question is: Is there such a ...
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693 views

Kickstarting an opamp for oscillating?

I have been building many different variations of op-amp oscillators but have come across a recurring issue that has manifested itself again in this VCO schematic: I find that when turning on my ...
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1answer
80 views

What is and how to measure the tuning port capacitance of a VCO

I was asked to check all the specifications of this Voltage Controlled Oscillator. I might have an idea of how to measure all the parameters except for one, the Tunning Port Capacitance. I think my ...
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2answers
492 views

VCO from a rectangular and triangular signal generator

I need to create the simplest rectangular and triangular signal VCO I can using op amps. The output frequency should be changeable between 1k and 15k. I should also be able to change the amplitude of ...
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1answer
138 views

Compact thermostat for VCO temperature stability

So I have a voltage controlled oscillator with an exponential input made using the THAT2181 VCA IC. The schematic is shown below - the THAT2181 IC is used to change the C4 capacitor charging current ...
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1answer
2k views

PWM and PPM using 555 timer

I get what PWM is and how it can be done using a 555 astable circuit. However I feel I don't completely get what PPM is how its circuit works. I understand the VCO circuit, but I don't see how it can ...
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1answer
134 views

Please explain the purpose of following circuit

This is the excerpt from the 2VCO synthesizer unit. Someone, please, can explain me what is this strange arrangement with VCO2 Out jack through the switch inside of it? I understand that when the Jack ...
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3answers
98 views

What is the purpose of the capacitors in this circuit that are in series with this VCO? [closed]

I am learning about how VCO modules operate and I am rekindling an old interest in electronics in general. For one particular VCO, the manufacturer has provided a circuit diagram. Does anybody know ...
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255 views

Relation between VCO's (Voltage Controled Oscillator's) Frequency and Voltage

I have a question that what is the relationship between the VCO generated frequency and applied volatage. Is there any formula which we can use to find the applied voltage and get the frequency ...
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1answer
643 views

Simulating varicap diode in LTSpice

I have been looking into making a voltage controlled oscillator using varicap diodes, however I have had hard time simulating the diodes in spice. Would anyone here have an idea how this would be ...
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1answer
157 views

Looking for an ultra wide modulation bandwidth, ultra linear VCO

I'm searching for a VCO in the 200-500 MHz area with 60 MHz modulation bandwidth which maintains 2% linearity (ideally better) in its tuning range. Would also prefer it to also hold 2% or better ...
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1answer
1k views

Mosfet Switched capacitor in LC tank

I need to coarse control the frequency of oscillation on a parallel resonant tank. The frequency band is in the 500kHz-1Mhz range, so the small capacitance of varactors doesn't suit the task. ...
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271 views

Principle for converting dual power supply to single

I was recently attempting to build a voltage controlled oscillator from this website: http://www.schmitzbits.de/vco4069.html. I struggled with it, for various reasons, and eventually found this ...
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238 views

Output waveform of VCO

This is a differential VCO which produces a sine waveform at the output taken across the drains of the MOSFETs. How should I interpret the drain current waveform at that point? Will it be a proper ...
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4answers
1k views

How does VCO in PLL in computer processor work?

In todays personal computers and notebooks, what is usually used as a Voltage-Controlled Oscillator for generating clock signal for processor? Is that a crystal rather than RC circuit? Is it tuned by ...
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1answer
132 views

Voltage gain of a vco

What should be the typical gain of an nmos only LC VCO? Should it be more than 100MHz/V or 200MHz/V or lesser than this? Which is more useful - keeping the gain high or low?
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2answers
349 views

PLL Design - Lock condition

I am designing a PLL. Can anyone explain to me what happens exactly in a lock condition? Should both the reference and input frequency be same in that state? My input freq is 25MHz and my VCO is ...
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2answers
197 views

Self resonant frequency of inductor in VCO

I am designing nmos only LC VCO in cadence TSMC180. I have chosen the self-resonant frequency of the inductor to be twice the working frequency of the LC tank. Is it a proper design for LC tank? Or do ...
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3answers
3k views

Can I make a VCO full audio range with only one capacitor?

I'm trying to make a VCO with a low voltage setup (3.3V), and i 'm using a mcp6002 op-amp. I'm controlling the frequency with an MCP4822 (dac). The problem is that i get a limited range of frequencies....
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3answers
201 views

Need help understanding this op amp/BJT configuration to troubleshoot why I'm reading different voltages than expected

I am building this VCO in an attempt to study it and I'm having trouble understanding the references section seen bellow. I have used a KIA431 that I 'stole' from a broken switching power supply on ...
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1answer
210 views

Help needed trying to build an audio sawtooth oscillator

I'm a total beginner hobbyist trying to understand the concept of an audio synthesizer, with a view to building one. Rather than just build a kit I'm keen to understand the concepts. Goal: build a ...
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975 views

Can I use a DAC to tune a VCO?

I found some FM transmitter circuits with the MAX2606 VCO. Example: Can I replace R1 with the DAC output from an AVR microcontroller? Or can I connect the DAC directly to Pin 3 of the MAX2606?
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198 views

BJT schmitt trigger has linear behavior on negative swings

I am currently building a VCO for an analog synthesizer. The circuit produces a triangle wave by taking a Schmitt trigger output and feeding it into an integrator. The constant output of the Schmitt ...
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2answers
413 views

(PLL) Why is it essential for VCO to continue oscillating when input is zero?

I have designed a simple PLL with current-starved ring VCO. The minimum frequency of oscillation for this VCO is zero since there is no current fed to ring of inverters when control voltage is zero. ...
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2answers
8k views

How to design a cheap sine-wave generator up to 200 MHz?

I want to make a cheap wideband oscillator for an antenna analyzer I'm designing. I want a simple sine wave over a wide frequency range. I don't want to use a DDS IC like the AD9851 because it's ...