The Moog Prodigy was a monophonic analogue synthesizer produced by Moog Music from 1979 to 1984. Of the 11,000 produced, versions released after 1981 included a control voltage/gate input on the back that allowed the VCF to be triggered and controlled by an external source. These later versions began at serial number 4610. The official model number of the instrument is 336. 336A would indicate a domestic (US) model, while a 336BX would indicate an export unit.
36-407: The housing is all metal except for the wooden side panels. The power supply is inside the instrument and the mains cable is detachable. The Prodigy featured two Voltage Controlled Oscillators (VCOs), one with a sawtooth waveform , a triangle waveform, and a pulse waveform, the second with a sawtooth, a triangle, and a square waveform. These waveforms could be detuned up or down by more than
72-464: A VCO can be used for frequency modulation (FM) or phase modulation (PM) by applying a modulating signal to the control input. A VCO is also an integral part of a phase-locked loop . VCOs are used in synthesizers to generate a waveform whose pitch can be adjusted by a voltage determined by a musical keyboard or other input. A voltage-to-frequency converter ( VFC ) is a special type of VCO designed to be very linear in frequency control over
108-504: A control system, the Laplace transforms of the above signals are useful. Tuning range, tuning gain and phase noise are the important characteristics of a VCO. Generally, low phase noise is preferred in a VCO. Tuning gain and noise present in the control signal affect the phase noise; high noise or high tuning gain imply more phase noise. Other important elements that determine the phase noise are sources of flicker noise (1/ f noise) in
144-429: A control voltage applied to the diode. Special-purpose variable-capacitance varactor diodes are available with well-characterized wide-ranging values of capacitance. A varactor is used to change the capacitance (and hence the frequency) of an LC tank. A varactor can also change loading on a crystal resonator and pull its resonant frequency. For low-frequency VCOs, other methods of varying the frequency (such as altering
180-439: A device fabricated with MOSFETs , for example, the gate capacitance must be charged before current can flow between the source and the drain. Thus, the output of every inverter in a ring oscillator changes within a finite amount of time after the input has changed. From here, it can be easily seen that adding more inverters to the chain increases the total gate delay, reducing the frequency of oscillation. The ring oscillator
216-433: A fifth, allowing for the creation of thick pads as well as atonal sounds. The two oscillators could be synchronized as well, then altered using the pitch wheel (in sync mode, the pitch wheel would alter the tonality of the sound, not the pitch. Roaring synth leads were made possible using this feature.) The Prodigy did not feature a white noise or pink noise generator. The voltage controlled 4-pole low-pass filter uses
252-454: A long distance, since the frequency will not drift or be affected by noise. Oscillators in this application may have sine or square wave outputs. Where the oscillator drives equipment that may generate radio-frequency interference, adding a varying voltage to its control input, called dithering , can disperse the interference spectrum to make it less objectionable (see spread spectrum clock ). Ring oscillator A ring oscillator
288-422: A loop, is not). Rather than having a single delay element, each inverter contributes to the delay of the signal around the ring of inverters, hence the name ring oscillator. Adding pairs of inverters to the ring increases the total delay and thereby decreases the oscillator frequency. Changing the supply voltage changes the delay through each inverter, with higher voltages typically decreasing the delay and increasing
324-784: A stable single-frequency clock. A digitally controlled oscillator based on a frequency synthesizer may serve as a digital alternative to analog voltage controlled oscillator circuits. VCOs are used in function generators , phase-locked loops including frequency synthesizers used in communication equipment and the production of electronic music , to generate variable tones in synthesizers . Function generators are low-frequency oscillators which feature multiple waveforms, typically sine, square, and triangle waves. Monolithic function generators are voltage-controlled. Analog phase-locked loops typically contain VCOs. High-frequency VCOs are usually used in phase-locked loops for radio receivers. Phase noise
360-414: A storage element and it is the basic building block of static random access memory or SRAM. The stages of the ring oscillator are often differential stages, that are more immune to external disturbances. This renders available also non-inverting stages. A ring oscillator can be made with a mix of inverting and non-inverting stages, provided the total number of inverting stages is odd. The oscillator period
396-462: A timing signal to synchronize operations in digital circuits. VCXO clock generators are used in many areas such as digital TV, modems, transmitters and computers. Design parameters for a VCXO clock generator are tuning voltage range, center frequency, frequency tuning range and the timing jitter of the output signal. Jitter is a form of phase noise that must be minimised in applications such as radio receivers, transmitters and measuring equipment. When
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#1732775610277432-415: A voltage input for fine control. The temperature is selected to be the turnover temperature : the temperature where small changes do not affect the resonance. The control voltage can be used to occasionally adjust the reference frequency to a NIST source. Sophisticated designs may also adjust the control voltage over time to compensate for crystal aging. A clock generator is an oscillator that provides
468-413: A voltage-controlled crystal oscillator can be varied a few tens of parts per million (ppm) over a control voltage range of typically 0 to 3 volts, because the high Q factor of the crystals allows frequency control over only a small range of frequencies. A temperature-compensated VCXO ( TCVCXO ) incorporates components that partially correct the dependence on temperature of the resonant frequency of
504-423: A wide range of input control voltages. VCOs can be generally categorized into two groups based on the type of waveform produced. A voltage-controlled capacitor is one method of making an LC oscillator vary its frequency in response to a control voltage. Any reverse-biased semiconductor diode displays a measure of voltage-dependent capacitance and can be used to change the frequency of an oscillator by varying
540-529: A wider selection of clock frequencies is needed the VCXO output can be passed through digital divider circuits to obtain lower frequencies or be fed to a phase-locked loop (PLL). ICs containing both a VCXO (for external crystal) and a PLL are available. A typical application is to provide clock frequencies in a range from 12 kHz to 96 kHz to an audio digital-to-analog converter . A frequency synthesizer generates precise and adjustable frequencies based on
576-413: Is a device composed of an odd number of NOT gates in a ring, whose output oscillates between two voltage levels, representing true and false . The NOT gates, or inverters, are attached in a chain and the output of the last inverter is fed back into the first. Because a single inverter computes the logical NOT of its input, it can be shown that the last output of a chain of an odd number of inverters
612-410: Is a member of the class of time-delay oscillators. A time-delay oscillator consists of an inverting amplifier with a delay element between the amplifier output and its input. The amplifier must have a gain greater than 1 at the intended oscillation frequency. Consider the initial case where the amplifier input and output voltages are momentarily balanced at a stable point. A small amount of noise can cause
648-495: Is in all cases equal to twice the sum of the individual delays of all stages. A ring oscillator only requires power to operate. Above a certain voltage, typical well below the threshold voltage of the MOSFETs used, oscillations begin spontaneously. To increase the frequency of oscillation, two methods are commonly used. First, making the ring from a smaller number of inverters results in a higher frequency of oscillation, with about
684-405: Is known to have used the synthesizer in some of the songs he made in the early 1990s. It has been used by many artists such as: Voltage-controlled oscillator A voltage-controlled oscillator ( VCO ) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently,
720-411: Is the logical NOT of the first input. The final output is asserted a finite amount of time after the first input is asserted and the feedback of the last output to the input causes oscillation. A circular chain composed of an even number of inverters cannot be used as a ring oscillator. The last output in this case is the same as the input. However, this configuration of inverter feedback can be used as
756-407: Is the most important specification in this application. Audio-frequency VCOs are used in analog music synthesizers. For these, sweep range, linearity, and distortion are often the most important specifications. Audio-frequency VCOs for use in musical contexts were largely superseded in the 1980s by their digital counterparts, digitally controlled oscillators (DCOs), due to their output stability in
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#1732775610277792-600: The Prodigy featured a triangle and square waveform, which could be routed to the VCO or VCF to create pitch or filter modulation effects. The Moog Source , which began production in 1981, featured internal workings very similar to the Prodigy in a much sleeker physical design that featured programmability, arpeggiator / sequencer and white noise. It inspired the name of British electronic band The Prodigy whilst recording their first album. The band's frontman, Liam Howlett ,
828-486: The advantages of having no off-chip components (expensive) or on-chip inductors (low yields on generic CMOS processes). Commonly used VCO circuits are the Clapp and Colpitts oscillators. The more widely used oscillator of the two is Colpitts and these oscillators are very similar in configuration. A voltage-controlled crystal oscillator ( VCXO ) is used for fine adjustment of the operating frequency. The frequency of
864-422: The amplifier output to rise slightly. After passing through the time-delay element, this small output voltage change will be presented to the amplifier input. The amplifier has a negative gain of greater than 1, so the output will change in the direction opposite to this input voltage. It will change by an amount larger than the input value, for a gain greater than 1. This amplified and reversed signal propagates from
900-435: The charging rate of a capacitor by means of a voltage-controlled current source ) are used (see function generator ). The frequency of a ring oscillator is controlled by varying either the supply voltage, the current available to each inverter stage, or the capacitive loading on each stage. VCOs are used in analog applications such as frequency modulation and frequency-shift keying . The functional relationship between
936-671: The circuit, the output power level, and the loaded Q factor of the resonator. (see Leeson's equation ). The low frequency flicker noise affects the phase noise because the flicker noise is heterodyned to the oscillator output frequency due to the non-linear transfer function of active devices. The effect of flicker noise can be reduced with negative feedback that linearizes the transfer function (for example, emitter degeneration ). VCOs generally have lower Q factor compared to similar fixed-frequency oscillators, and so suffer more jitter . The jitter can be made low enough for many applications (such as driving an ASIC), in which case VCOs enjoy
972-504: The control voltage and the output frequency for a VCO (especially those used at radio frequency ) may not be linear, but over small ranges, the relationship is approximately linear, and linear control theory can be used. A voltage-to-frequency converter (VFC) is a special type of VCO designed to be very linear over a wide range of input voltages. Modeling for VCOs is often not concerned with the amplitude or shape (sinewave, triangle wave, sawtooth) but rather its instantaneous phase. In effect,
1008-423: The crystal. A smaller range of voltage control then suffices to stabilize the oscillator frequency in applications where temperature varies, such as heat buildup inside a transmitter . Placing the oscillator in a crystal oven at a constant but higher-than-ambient temperature is another way to stabilize oscillator frequency. High stability crystal oscillator references often place the crystal in an oven and use
1044-400: The face of temperature changes during operation. Since the 1990s, musical software has become the dominant sound-generating method. Voltage-to-frequency converters are voltage-controlled oscillators with a highly linear relation between applied voltage and frequency. They are used to convert a slow analog signal (such as from a temperature transducer) to a signal suitable for transmission over
1080-413: The focus is not on the time-domain signal A sin( ωt + θ 0 ) but rather the argument of the sine function (the phase). Consequently, modeling is often done in the phase domain. The instantaneous frequency of a VCO is often modeled as a linear relationship with its instantaneous control voltage. The output phase of the oscillator is the integral of the instantaneous frequency. For analyzing
1116-433: The initial noise may not be square as it grows, but it will become square as the amplifier reaches its output limits. The ring oscillator is a distributed version of the time-delay oscillator. The ring oscillator uses an odd number of inverters to give the effect of a single inverting amplifier with a gain of greater than one (Although, a single inverter in a loop is stable and a ring oscillator with odd number or inverters in
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1152-486: The oscillator frequency. Vratislav describes some methods of frequency-stability and power consumption improving of the CMOS ring-oscillator. If t represents the time delay for a single inverter and n represents the number of inverters in the inverter chain, then the frequency of oscillation is given by: The period of a ring oscillator varies in a random manner as T+T' where T' is a random value. In high-quality circuits,
1188-421: The output through the time-delay and back to the input where it is amplified and inverted again. The result of this sequential loop is a square-wave signal at the amplifier output with the period of each half of the square wave equal to the time delay. The square wave will grow until the amplifier output voltage reaches its limits, where it will stabilize. A more exact analysis will show that the wave that grows from
1224-415: The range of T' is relatively small compared to the average period T. This variation in oscillator period is called jitter . Local temperature effects cause the period of a ring oscillator to wander above and below the long-term average period. When the local silicon is cold, the propagation delay is slightly shorter, causing the ring oscillator to run at a slightly higher frequency, which eventually raises
1260-409: The same power consumption. Second, the supply voltage may be increased. In circuits where this method can be applied, it reduces the propagation delay through the chain of stages, increasing both the frequency of the oscillation and the current consumed. To understand the operation of a ring oscillator, one must first understand gate delay . In a physical device, no gate can switch instantaneously. In
1296-427: The typical Moog transistor ladder filter design. There is a dedicated 3-stage ADR envelope controller (ADR short for Attack Decay Release). The Prodigy was capable of a full range of synthetic sounds, from a gentle whistle or flute in the upper ranges, to sub-sonic bass. The voltage controlled amplifier (VCA) was controllable only via a second 3-stage ADR envelope controller. The low frequency oscillator (LFO) of
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