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AC to DC & DC to DC
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Data Bus Circuits
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RF Converter Circuits
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Video Wall circuits
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8051 / 8052
PCB CAD Software
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555 Timer Circuits
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DIY HV Variable Cap
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Digital Signal Integrity
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4 Band Resistor
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Volt Controlled Oscillator Circuits
Volt Controlled Oscillator Circuits
The 566 can be wired as a positive or negative ramp generator. In the positive ramp generator, the external transistor driven by the Pin 3 output rapidly discharges Cl at the end of the charging period so that charging can resume instantaneously. The pnp transistor of the negative ramp generator likewise rapidly charges the timing capacitor Cl...
Simple voltage controlled oscillator
With the component values shown, the oscillator has a frequency of 8 kHz. When an input signal is applied to the base of Ql the current flowing through Ql is varied, thus varying the time required to charge Cl. Due to the phase inversion in Ql the direction of output frequency change is 180 degrees out of phase with the input signal
A voltage-variable capacitance tuning diode is placed in series with the crystal feedback path. Changing the voltage on VR varies the luning diode capacitance and tunes the oscillator. The 510-KO resistor, R1, establishes a reference voltage for VR -ground is used in this example. A 100-KO resistor, R2, isolates the tuning voltage from the...
This TMOS VCO operates in push-pull to produce 4 Wot 70 MHz. It consists of two MFE930 TMOS devices in a balanced VCO that generally provide better linearity than the single-ended types. Varactors are not used because the design takes advantage of the large change in Miller capacitance, G?ss, that is available in TMOS gate structures.
You can transform a 7415124 multivibrator into a wideband VCO by replacing it conventional fixed capacitor with a variable-capacitance diode. The only disadvantage of this scheme is the 30-V biasing voltage that the diode requires. Capacitors C1 and C2 couple the Philips BB909A variable-capacitance diode to the 745124.
This circuit uses the output of the IGL8049 to control the frequency of the IGL3038 waveform generator; the 741 op amp is used to linearize the voltage-frequency response. The input voltage to the 8049 can be, for example, from the horizontal sweep signal of an oscilloscope; the output of the 8038 will then sweep logarithmically across the...
This simple circuit can convert a single supply voltage, such as a battery, into a bipolar supply. Sense resistors Rl and R2 establish relative magnitudes for the resulting positive and negative voltages. Their rail-to-rail value, of course, equals VsUPPLYÂ· R4 and R5 represent the load impedances. For example, equalvalue sense resistors...
At startup, the voltage in the trigger input at pin 2 is less than the trigger level voltage, "13 VDD. caus ing the timer to be triggered via pin 2. The output of the timer at pin 3 becomes high, allowing capacitor c, to charge very rapidly through diode Dl and resistor Rl. When capacitor C, charges to the upper threshold voltage 2 /3 V00, the...
The output frequency of the VCO, U1, varies inversely with the input voltage. With a 1 "V input, the oscillator output frequency is about 1500 Hz; with a 5-V input, the output frequency drops to around 300 Hz. The output frequency range of U1 can be altered by varying the values of C1, R2, and R3. Increasing the value of any those three...
Video Line Bar Generator Circuit
A 555 and a dual 556 timer generate a rudimentary video signal, as shown in the schematic. The first timer generates 4.7-8 synch pulses operating in the astable mode with a 64-8 period. The second timer generates a delay pulse, which triggers the third timer to generate a bar,
Sinusoidal 3Hz To 300Khz Vco Circuit
This circuit uses Analog Devices` AD639 universal trigonometric function generator to convert a triangle waveform, the basic waveform of the VCO itself, into a very low-distortion sine wave. By using the AD639 in its frequency tripler mode , the frequency range 3 Hz to 300 kHz is now covered. The circuit has been drawn here--so that the...
Vco Circuit Circuit
The output frequency of this simple low-cost active voltage-controlled oscillator circuit is based upon the inherent frequency dependent characteristics of our operational amplifier. The oscillator circuit shown uses a TL082 op amp. When power is applied, the circuit generates a sinusoidal wave.
Voltage controlled ramp generator
The current source formed by Ql in conjunction with capacitor Cl set the duration time of the ramp. As the positive dc voltage at the gate is changed, the peak point firing voltage of the PUT is changed, which changes the duration time.
A Colpitts VCO for Wideband (0.952.15 GHz)
Modern set-top DBS TV tuners require high performance, broadband voltage control oscillator (VCO) designs at a competitive cost.To meet these goals, design engineers are challenged to create high performance, low-cost VCOs.
1-Hz to 100-MHz VFC features 160-dB dynamic range
The VFC (voltage-to-frequency-converter) circuit in Figure 1 achieves a wider dynamic range and a higher full-scale output frequency100 MHz with 10% overrange to 110 MHzby a factor of 10 over any commercially available converter.
µC-based circuit performs frequency multiplication
The traditional frequency multiplier requires many elements: a phase comparator to detect the phase error between the input and the output signals, a lowpass filter to convert the phase error to a dc control signal, a VCO to generate the output, and a divider to set up the multiple ratio. The circuit in Figure 1 uses a different approach to...
µC forms FM oscillator
A project required an inexpensive oscillator whose frequency increased step by step from 200 to 400 Hz and then decreased to 200 Hz. The first step was to design a VCO with a staircase driver. However, this approach entailed at least four ICs and many discrete components. An alternative method (Figure 1) requires only one 16-pin µC (an...
Circuit allows high-speed clock multiplication
In theory, synchronous clock multiplication is an easy task. A simple PLL with two digital dividersone inserted just after the VCO (voltage-controlled oscillator) and the second one placed directly at the input of the phase detectormay do the job. The flexibility of such a configuration allows for clock multiplication by any rational number.
Clock-recovery scheme suits low-SNR systems
A clock-recovery architecture can operate with NRZ digital signals, even at low SNRs. A clock-recovery subsystem is based on a PLL comprising a phase comparator, a loop filter, and a voltage-controlled oscillator (VCO).
LED driver as fault monitor
Using just four transistors and six resistors, this circuit provides switchable, constant-current drive for an LED and indicates both open- and short-circuit fault conditions (Figure 1). And there`s a bonus, too. Control signal VCONT switches the LED on and off. When VCONT is high, Q1 and the LED are off. When VCONT is as low as 0V, Q1 turns on...
Processor`s PWM output controls LCD/LED driver
The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is the logic-supply voltage. The control circuit`s output impedance is the sum of the...
Circuit tests VCOM drivers
Flat-panel LCD monitors offer excellent image quality and more compact form factor than CRTshence, their steadily increasing popularity. Unfortunately, the complexity of their manufacturing process makes LCD monitors considerably more expensive than CRTs. The amplifier that drives VCOM, the voltage on the backplane of the LCD panel, must be able...
NTE789 Stereo Multiplex Decoder
Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a lowdistortion preamplifier and simultaneously applied to both signal, generated by a local voltagecontrolled oscillator (VCO), is counted down by two frequency dividers to a 38kHz signal and to two 19kHz pilottone supplied by the FM detector...
Wave Multiplier for music synthesizers
For the primary multiplier, the "folder", connect the input to the triangle wave output of a VCO. Connect a LFO, envelope generator or even a DC voltage to the folds input. The result will be a harmonically rich signal at the "F out" output. A second input based on a lag circuit allows square waves and other hard-edged waveforms to be used as...
Inverters form three-phase VCO
The inspiration for the VCO in Figure 1 came from Texas Instruments application notes of years ago, detailing the use of unbuffered U-type inverters for use in ring oscillators. The application notes circuit consists of only the inverters. The circuit generates relatively squarish waveforms. Any ring oscillators operation depends on the...
VCO produces output frequencies
The circuit in Figure 1 is a quadrature-output VCO that provides both positive and negative output frequencies, depending on the polarity of the control-voltage input. The circuit provides a function that designers traditionally implement in analog music-effects units, such as Bode/Moog frequency shifters. Bode/Moog shifters use...
programmable logic VCO
A VCO (voltage-controlled oscillator) is an analog circuit, so you cannot find it in the libraries for the design of digital programmable chips. When you need such a circuit for synchronization or clock multiplication, you need to find a circuit that works with the standard digital functions, such as AND and NAND. Several possibilities exist for...
Multilayer capacitor doubles as varactor
The circuit is also an inexpensive VCO (voltage-controlled oscillator) with only five components. Many types of ceramic capacitors for surface-mount placement are on the market. The parts become continually smaller because of space problems on the board, and the capacitance values continually increase to compete with more expensive...
Voltage programmable square wave generator
Here's another daft yet interesting PIC12F675 idea I came up with. When I wanted to show someone how logic gates worked I could only find a NAND gate which wasn't very handy for demonstrating AND's OR's, NOR's and ExOR's. I also wanted to have a play with the A/D converter on the 12F675 so I came up with the idea of a PIC that could function as...
200mW FM transmitter
Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW...
VCO with NE567
Who would like to build a sidetone oscillator with a minimum amount of parts should try the NE567 integrated circuit. The NE567 is a PLL circuit with an internal VCO for a operating frequency less than 500 kHz and it is normally used as an audio tone decoder. The VCO frequency is adjustable by two passive components only. For a 750 Hz sidetone...
1.2GHz Voltage Controlled Oscillator With Linear Modulation
Since high frequency voltage-controlled oscillators, or VCOs, are not easy to construct, Maxim ( has produced an integrated 1. 2GHz oscillator, the MAX2754. The center frequency is set using the TUNE input, and a linear modulation input allows the frequency to be modulated. The IC is available in an 8-pin µMAX package, operates from a supply of be
Astable Oscillator Circuits
Colpitts Oscillator Circuits
Crystal Oscillator Circuits
Hartley Oscillator Circuits
RF Oscillator Circuits
Sine Wave Oscillator Circuits
Square Wave Oscillator Circuits
Wein Bridge Oscillator Circuits
Pierce Oscillator Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
DIY HV Variable Capacitor
DIY PMA Alternator Plans
Digital Signal Integrity