# Questions tagged [vco]

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

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117 views

### How can an audio signal with varying frequency be modulated using FM? [closed]

An audio signal can have varying frequency and amplitude and both are the part of the information. As I understand it, frequency modulation is a technique where the frequency of the carrier wave is ...
17 views

### Transfer function of noise from Vtune of VCO to its output phase noise using VerilogA model

I am using the code below for VCO, and it is pretty standard and straightforward. I want to make sure that the noise transfer function from control voltage to phase noise is correct, as I am going to ...
1 vote
59 views

### Designing a sawtooth VCO

Beginner here. I am trying to build a sawtooth VCO that runs on 5V, based on an op-amp integrator. See the design and output (Vout of the op-amp) below. For this circuit, the input voltage needs to ...
179 views

### Variable frequency sine generator

What is an simple option to generate a low freq. sine in range 10Hz to 200Hz? I tried to make a triangle and integrate it but I obtained a huge difference in amplitude as I change the triangle ...
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### Is it legitimate to apply reset logic to inputs only?

Let us consider this module for FPGA implementation: ...
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### Tips on Building An Analog VCO

I am attempting to build an analog VCO. Many of the resources I see online implement a 555 timer, but I am trying to avoid that, solely for the sake of learning how to do this in purely analog. Here ...
77 views

### How can I generate an impulse-like response to a centered wave crossing upward past 0V?

I am a newbie audio electronics hobbyist. Some collaborator friends and I were thinking about a useful control voltage application, and thought that a spiky 'impulse-like' response to an input voltage ...
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### How to debug unexpected behavior on voltage-controlled oscillator PCBA?

I designed a circuit for a voltage-controlled oscillator (VCO) for use in a synth and had it fabricated and assembled as a PCBA. I got three assemblies back and while two behave exactly to spec (and ...
1 vote
100 views

I designed and tested a PCB with a PLL circuit. The goal is to lock on the reference signal which is a square wave. The problem I am having is that the signal of the N-counter shows no response, just ...
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189 views

### FSK modulation and inverting mark and space bits

Quick theory to application question. In Frequency shift keying we usually have the output of a sequence generator into a VCO, then this leads to a high frequency for the mark bit and a lower ...
136 views

### Generating an analog sawtooth ramp for PWM

I came across the circuit below: Source I can't seem to understand how the circuit works. They even say that one can set the maximum duty cycle. Kindly explain to me how the circuit works. I would ...
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509 views

### Problems Comparator II of this CD4046 for LTspice

I downloaded a CD4046B model from user ale_t, which can be found here: https://www.electro-tech-online.com/threads/new-spice-model-for-cd4046b-phase-locked-loop-ic.149093/ However, the Phase ...
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197 views

I am working on a PLL design. I am at the research stage now. I am confused about the PLL input frequency range. This frequency has to remain constant. If this input frequency stays constant, how can ...
543 views

### Frequency multiplication with PLL circuit

I am currently working on frequency multiplication with a PLL circuit. I want to give it an input frequency of 10 kHz to 100 kHz and I want to get 160 kHz to 1.6 MHz from the VCO output. That's a ...
165 views

### Modern temperature compensation of 1 V/oct VCOs

With Akaneohm Tempco resistors going out of production, I have been searching for alternative ways to reliably build a VCO that does not drift with temperature. I have been searching around, but I can ...
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542 views

### Micro CAP Error: Internal time step too small in transient analysis

i try make simple VCO in Micro-cap 12. But when i but when i try to run transient analysis and i get an error. X1 and X2 is a mcp6001 and Q1 is a BC548B(from standard library) UPD: after set ...
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I understand that most, if not all, SDRs use direct conversion, since an SDR can receive several channels simultaneously. So how does tuning the VCO work? Let's assume for simplicity that I need to ...
101 views

### Colpitts VCO design problem

I have found a design to Colpitts VCO to get a sinusoidal output start with 900 MHz - 1100 MHz but it doesn't work. this is the link below for the project that I have simulate it, but I can't get ...
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1 vote
338 views

### Question about the Verilog-A implementation of a VCO

I am learning verilog-A to model analog circuits. One of the examples given in the book is that of a voltage-controlled oscillator (VCO). The book says the following about how the VCO can be modelled (...
290 views

### Changing varactor capacitance based on different frequencies

I am working on a project that uses a varactor diode in a VCO to output a certain frequency. As I understand it, changing the voltage amplitude changes the capacitance of the varactor diode. The input,...
1 vote
28 views

### STF from VCO Signal Flow Graph

I've been looking at this paper that uses a VCO for a resistive sensor readout and I'm rather confused about how to derive this transfer function they have from their signal flow graph. In their work ...
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162 views

### Problems increasing VCO frequency above datasheet recommendations

Firstly, yes I contacted ST for answers. Until now, no answer. I'm using STM32F429 MCU and embedded USB FS PHY. To keep the 48 MHz USB PHY clock the maximum PLL clock that I can achieve is 168 MHz, ...
215 views

### Type of VCO that generates square waves

According to Wikipedia, there are two types of VCOs. Linear or harmonic oscillators generate a sinusoidal waveform. Relaxation oscillators can generate a sawtooth or triangular waveform. What are ...
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1 vote
295 views

### How can I build a current controlled 50% duty cycle oscillator from two CMOS inverters?

I am in need of a current controlled audio range (output around 1000 Hz) oscillator/multivibrator circuit. To make the result sound nice, I want to oscillator to have a 50% or near 50% duty cycle. ...
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1 vote
188 views

### Should I be concerned with the higher current draw coming from a part of my circuit design, and if so, how should I limit it in my circumstance?

I'm designing a voltage controlled oscillator for a modular synthesizer. My planned range for this circuit is anywhere between 37Hz to ~20kHz. Here's a schematic of it I made with the Falstad ...
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1 vote
340 views

### VCO generating a lot of electrical noise, picked up by ultrasonic transducer

In my setup, I have a VCO CD4046 Phase Locked Loop IC generating a square wave, and an ultrasonic transducer set that transmits and receives that setup. You can imagine it looking something like this. ...
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1 vote
90 views

### Differential voltage to frequency

Edited to clarify some questions I’m working on a design that will take a 0.5V-4V signal from a laser displacement sensor (Keyence Il-1000) and convert it to a frequency signal (0.1-2Mhz) for input to ...
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### ~3400 ppm/C resistor replacement/substitute?

I am working on reviving an old synth design (Transcendent 2000 for those interested) and the VCO and VCF both rely on high ppm/C resistors to compensate for temperature changes. I can include the ...
131 views

### PLL and VCO example of a reference tone's frequency muliplied by 12000 to generate a master clock

A free project RAM Platter Hybrid aims to generate a master clock from a tone which is 12000 times lower in frequency. The reference tone is 1 kHz at its central frequency. It will have a minimum of 0 ...
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### DDS example of a reference tone's frequency muliplied by 12000 to generate a master clock

A free project RAM Platter Hybrid aims to generate a master clock from a tone which is 12000 times lower in frequency. The reference tone is 1 kHz at its central frequency. It will have a minimum of 0 ...
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1 vote
541 views

### Voltage controlled oscillator with a MOSFET

Is it a good idea to use a normal MOSFET as a varactor for a variable signal generator? For example: I have an IRFZ44N and the datasheets says it has an input capacitance of 1470 pF. Can I use that ...
321 views

### VCO from near-0 Hz to 100 MHz [closed]

Anyone know of a VCO which can range from close to 0 Hz up to around 100 MHz ? I have tried the 4046A IC, however am having trouble getting enough high frequency out of it.
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### Spurs at 40 kHz frequency multiples

I have designed a PLL using an ADF4106 and a VCO. I have taken references from CN0290. I have designed the loop filter using the ADSimmPll tool from Analog Devices. I got below values from ADSimmPll ...
125 views

### VCO tuning voltage range starting from higher than 0 V

I have seen some VCO datasheets. In every datasheet, I see that the tuning voltage range starts from some value above 0 V (like 0.5 V, 1 V etc). So, what would be the frequency at 0 V? And why do they ...
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761 views

### Making a simple 555 sawtooth VCO stable?

I have figured out how to make a sawtooth VCO using a 555 IC , by using a current mirror. The issues I am having is I can't make it stable at all. Its having random issues like it randomly changes ...
764 views

### Struggling to understand how a phase locked loop reaches lock

I have a basic question regarding PLLs and how they actually achieve lock. I was told that the PLLs go into the lock when the output of a phase detector is zero, therefore to drive VCO an integrator ...
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### How do different octaves sound different in the presence of a low-pass filter in a synthesizer?

Per my understanding, when playing a certain pitch, say 440 Hz (middle C), the VCOs will produce their corresponding waveforms (say sawtooth) at that frequency. Because of the characteristics of the ...
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305 views

### Can I use LVCMOS output crystal in 50 ohm system

I have a 50 ohm clocking system in a very low noise environment (RADAR). I want to use a Abracon 100 MHz VCXO (this one), which has a 3.3V LVCMOS output. Below you can see the block diagram of the ...
220 views

### Noisy out from the PLL

I have designed a PLL using an ADF4106 and a VCO. I have taken references from CN0290. I am able to get the desired output from the design, but there are other unwanted peaks in the output. I have ...
49 views

### VCO output is its maximum frequency

I am trying to design PLL for generating 122.8MHz from 40 MHz REFIN. I am following the CN0290 EVM reference for the design. I have used CVCO33CL-0110-0150 VCO in the place of VCXO in EVM. When I am ...
77 views

I am trying to design PLL for generating 122.8MHz from 40 MHz REFIN. I am following the CN0290 EVM reference for design. As you can see, in the EVM REF_INPUT is of 10MHz and 100MHz frequency is being ...
57 views

### Fractional output from integral PLL

Is it possible to get a fractional output from an integral output PLL? I am using ADF4106. Is it possible to generate 122.8MHz using this PLL?
316 views

### Phase relationship of multiple Fractional-N PLLs with same reference clock

I think I understand the general operation of PLLs in the case where a single reference clock generates a single output clock. Once the PLL is locked, there is a deterministic relationship between the ...
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### What is the output of this VCO?

I am using ROS-43-119+ from Mini-circuits. I need a VCO that can generate a 40MHz frequency. ROS-43-119+ can generate my required frequency by controlling the tuning voltage. I need sinewave output ...
171 views

### VCXO output frequency tuning

I am planning to use this VCXO CVSS-945-100.000 to generate 40MHz by providing the control voltage from a PLL. The datasheet mentions control voltage as below: Is it possible to generate 40MHz using ...
2k views

### Loop filter bandwidth calculation

I am trying to Design a PLL using ADF4106 and VCXO. The reference frequency is 10MHz and VCXO output is 40MHz. I need to design a Loop filter for converting charge-pump voltage from PLL into Control ...
266 views

### Differences between phase locked loop on PCB and on breadboard

I have a question with regard to the differences between a PLL on a PCB and on a breadboard. In this test, I have connected the output of the amplifier (LMH6503) to both the PLL on the PCB and the PLL ...
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### Can someone explain this trend of Control Voltage Vs Output Freq? Circuit configured:- 555 IC as a VCO

So, in my Master's, while going through a lab for analog electronics, we were given this seemingly pointless task of plotting Control Voltage vs Output Freq when a 555 IC is configured as a VCO. The ...
118 views

### why the control voltage of VCO in CP PLL oscillates?

I built a verilogA model for every block used in PLL, I replaced a verilogA model for VCO with a designed one but, I got oscillations imposed on the control voltage as shown below. Fdiv is the ...
233 views

### Using PLL as resonance tracker

Edit: Re-re-formulated :) I'm developing a resonant circuit with its resonant frequency around 3 GHz. I am constantly tuning this resonance frequency by an unknown amount. How can I read out the ...