Common questions

What is a VCO circuit?


What is a VCO circuit?

A voltage-controlled oscillator (VCO) is an oscillator circuit whose frequency can be controlled or varied by a DC input voltage. This type of circuit is also called a voltage-to-frequency converter (VFC). The output waveform from the VCO may be sine, square, or other waveshape depending on the circuit design.

What is the transfer function of VCO?

Its purpose is to force the VCO to replicate and track the frequency and phase at the input when in lock. The PLL is a control system allowing one oscillator to track with another. It is possible to have a phase offset between input and output, but when locked, the frequencies must exactly track.

What is current starved VCO?

CURRENT STARVED VCO. A ring oscillator is comprised of a number of delay stages, with the output of the last stage fed back to the input of the first. To achieve oscillation, the ring must provide a phase shift of 2π and have unity voltage gain at the oscillation frequency.

Which filter is used in VCO?

Which filter is used in VCO? Explanation: The loop filter used in the VCO can be one of the three types of filter shown above.

What happens when VCO output is 90?

What happens when VCO output is 90o out of phase with respect to input signal? Explanation: The error voltage is zero when the phase shift between the two inputs is 90o. So, for the perfect lock, the VCO output should be 90o out of phase with respect to the input signal.

What starved today?

But current starving is the motivation to construct low power circuits by shrinking the size, voltage and power. Current limiting is the act to keep the current under a certain limit to prevent destructions.

What is meant by current starved inverter?

Using this design technique (current-starved), the current is controlled in each stage of the ring oscillator, achieving a wide frequency of operation. This design operates up to approximately 350MHz and the output is clamped to 1.4V.

Which IC is used as VCO?

Voltage controlled oscillator using LM566 IC It can be used to generates square and triangle waveforms simultaneously. The frequency of the output waveform can be adjusted using an external control voltage. The output frequency can be also programmed using a set of external resistor and capacitor.

What is PLL?

A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal. PLLs are used to generate, stabilize, modulate, demodulate, filter or recover a signal from a “noisy” communications channel where data has been interrupted.

What are the requirements for a VCO circuit?

VCO requirements. These are some of the main requirements that need to be known from the outset of the design of the VCO. Careful optimisation of the Q of the tuned circuit, especially using varactor diodes with as high a Q as possible, choice of active device, optimisation of the feedback within the oscillator.

Can a VCO use both bipolar and FET transistors?

It is possible to use both bipolar devices and FETs within a VCO, using the same basic circuit topologies. The bipolar transistor has a low input impedance and is current driven, while the FET has a high input impedance and is voltage driven.

What happens when the frequency of a VCO is increased?

Tuning flatness – As the VCO frequency range is increased, the difficulty to achieve a flat output power is increased. Adding an output filter to suppress harmonics may in somecases degrade power output flatness. The drive level should consider the trade-off between harmonic content, oscillator stability, and noise.

What is the frequency of a VFO circuit?

The circuit, with the values shown, operates between 4.570 and 4.646 MHz. To change the values for the frequency you want, multiply the values by the ratio of your desired frequency to 4.570 MHz.