Top Circuits Page 21
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Requiring only 10uA of quiescent current, the circuit of (Fig. 62-1 (a)) produces only 0.1ohm ON-resis-tance...
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Two complementary MOSFETs are used to deliver 20 W into 8 . A TL071 op amp is used as an input amplifier. The MOSFETs should be heatsinked with a heatsink of better than 5C/W capability...
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A MOSFET is used as a wideband buffer amplifier. T1 is wound on a toroid of approximately /f diameter, with material suitable for frequency (usually 1- to 20-MHz range). The turns ratio should be about 4:1 depending on load impedance. Typically, at 4 MHz,....
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A charge pump is a simple means of generating a low-power voltage supply of opposite polarity from the main supply. The 74Cl4 IC is a self-oscillating driver for the MOSFET power switch. It produces a pulse width of 6.5 p,s at a repetition frequency of....
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The LM39X4 acts as a LED-driving vol-tometer that has its basic maximum and minimum readings determined by the values of R2 and RV2. When correctly adjusted, the unit actually covers the 2 volt to 3 volt range, but it is made to read a supply voltage span of....
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A zener diode placed in series with a voltmeter will prevent the meter from reading until the applied voltage exceeds the zener voltage..
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The sensing circuit rapidly disconnects the battery voltage and load whenever the voltage drops below a preset threshold. One-way operation prevents the circuit from reconnecting the load if the voltage should then rise above the threshold. Cl ensures that....
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When Sl is depressed, Cl begins to charge to the supply voltage. That places a forward bias on the gate of Ql turning it on and supplying current to load resistor RL. When the charge on Clleaks off, the transistor shuts off, cutting off current to the....
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If a NiCad battery is discharged to a point at which the lowest capacity cell becomes fully discharged and reverses polarity, that cell will usually short internally and become unusable. To prevent this type of damage, this circuit detects a one-cell drop of....
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Circuit provides a minimum of 7 V until the 9-V battery voltage falls to less than 2 V. When the battery voltage is above 7 V, the MAX630"s IC pin is low, putting it into the shutdown mode which draws only 10 nA. When the battery voltage falls to 7 V, the....
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Most of the circuitry is contained in the LM3914 dot/bar-graph driver IC chip. In addition to the comparator circuitry within the package, it also contains a stable reference supply and the drivers for the LEDs. Resistor R2 acts as the current limiter....
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Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery"s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage....
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To prevent battery damage due to over -disc barge, a low-voltage detector and switch should be included in the design of the battery backup circuit. The detector circuit should consume extremely low current. The switch should exlnbit a low-voltage drop and....
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NiCad batteries are excellent rechargeable power sources for portable equipment, but ~care must be taken to ensure that the batteries are not damaged by overdischarge. Specifically, a NiCad battery should not be discharged to the point where the polarity....
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The test circuit gives an indication of the capacity remaining in a battery. By noting the time in seconds that the LED remains on after you depress the test switch Sl. The circuit has proven reliable in testing NiCad-, carbon-, and alkaline-type....
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A common need in many systems is to obtain positive and negative supplies from a single battery. Where current requirements are small, the circuit shown is a simple solution. It provides symmetrical ± output voltages, both equal to one half the input....
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The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes....
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A tricolor LED, acts as the visual indicator of the voltage level. The voltage to be measured is connected to the two comparators in parallel. The first 20-KO trimmer defines a voltage between ±5 V and this becomes the full-scale value of the reference....
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Any potential from 1 to 15 V can be monitored with this circuit. Two lamps alert any undesirable variation. The voltage differential from lamp tum-on to tum-off is about 0.2 Vat any setting. High and low set points are independent of each other. The SCRs....
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This voltmeter exploits a number of tbe CA3160 BiMOS op amp"s useful characteristics. The available voltage ranges from 10 mV to 300 V. Powered by a single 8.4-V mercury battery, this circuit, with zero input, consumes approximately 500 p,A. ..
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This de voltmeter, with high input resistance, uses a CA3130 BiMOS op amp and measures voltages from 10 m V to 300 V. Resistors R12 and Rl4 are used individually to calibrate tbe meter for full:scale deflection. ..
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A2N3819 FETprovides a solid-state VOM. The 2N3819 acts as a cathode follower in a VOM. The bias offset (meter null) is obtained with R14 and R12 sets full-scale calibration. R2 through R9 should total about 10 MO. ..
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This schematic shows a peak-reading diode voltmeter driven by two stages of amplification. A 100-ILF capacitor provides a fairly large time constant, which results in satisfactory meter damping. The limited differential output voltage coupled with an....
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If the battery voltage exceeds about 11 V, current flows through R1, D1, and R2. The voltage produced as a result of current flow through R2 is sufficient to bias transistor Q1 into conduction. That places the collector voltage of Q1 virtually at....
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Capacitor C4 couples the output of U1 to a simple attenuator, which is used to provide a loss of 0 dB, 20 dB, or 40 dB, depending on the setting of range switch Sl. The circuits sensitivity is 10-V rms for fullscale deflection, so the attenuator gives....
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Input terminal VIN is connected to the +V line of tbe circuit that the indicator is to monitor, and the grounds of botb circuits are connected togetber. The position of potentiometer Rl"s wiper determines Q1"s base voltage. As long as the transistor....
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This circuit uses only one JC, either 1, LM393 dual comparator or 1/z, LM339 quad comparator. RV1 and RV3 set the full scale reference voltage, and RV2 and RV4 set the switching thresholds to a value between 0 V and the full-scale reference. ..
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This circuit will allow a multimeter to display the positive or negative peaks of an incoming signal. A 741, JC1, is used in the noninverting mode with R1 defining the input impedance. D1 or D2 will conduct on a positive or negative peak, charging C2 until....
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This current source has continuous control of the magnitude and polarity of its amplifier gain and needs only one voltage reference. The circuit includes reference ~, voltage-amplifier circuit A1 with gainsetting resistor Rs, and bootstrap-follower....
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This circuit shows a simple method of achieving a voltage reference which can be trimmed using an 8bit DAC with an on-chip voltage reference. The analogue output from the DAC drives the trim pin of the ZNREF025 via a resistor, R,. When Rs = 0, this circuit....
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The voltage to be measured is digitized in an analog-to-digital (A/D) converter and then displayed in three decimal d..
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The current range in multimeters, particularly the more inexpensive ones, is restricted by the load limits of the internal..
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This circuit detects brief shorts or opens. When S2 is in the up position, the circuit indicates if there is or..
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The adjustable voltage monitor can be used to check whether the voltage in a circuit remains within a given range. If the dc voltage is less than the voltage at pin 5 of-Ul-B, then LED 1 will light. If the voltage is over 5V, LED2 will light. If the voltage....
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The pseudorandom sequencer drives a solid-state relay. If you power a low-wattage lamp from the re..
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Using a 555 timer to drive a CMOS counter, this device uses RCA CA3079 zero-voltage switch to control triacs TR1 through..
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Up to 100 lights, LEDs, or optocoupler triac circuits can be sequentially activated by this circuit. One (Ul) 4017 decode co..
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Up to six lights can be sequentially flashed using this circuit. LED1 through LED6 can be replaced by optocouplers (MOC3010..
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A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017s first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that the IC normally delivers.....
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The light sequencer uses two ICs and 10 SCRs to create.an ac sequencer. The first 10, a 555 timer, is used to provide clock pulses for 102. The 10 is configured as an astable multivibrator, and its output is on pin 3. Capacitors CI and 04, along with....
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Integrated circuit Ul (a 555 oscillator/timer) is wired as a conventional pulse generator. The frequency of the pulse generator is controlled by potentiometer Rll. Resistor R2 puts areasonable limit on the highest speed attainable. The output of the pulse....
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This circuit is useful in amateur radio VHF and UHF work where a mast-mounted antenna preamp is used for receiving. The kit controls T-R switching and change-over relay sequencing so that high RF levels are prevented ..
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In this circuit, an additional exclusive-OR gate is connected after the modulo-2 feedback, with CI and R2 applying the supply turn-on ramp into the feedback loop. This provides sufficient transient signal so that the PRBS generator can self-start a....
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The incoming RGB inputs are terminated with resistors Rl, R2, and R3 and potentiometers RVl, RV2, and RV3. These provide input impedances of approximately 75 0. The presets should be adjusted to provide a maximum input of 1 V pk-pk into the MC1377. The....
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This circuit extracts the sync pulses from a video signal over a wide range of amplitudes and operates a single +15 V supply. IC1 buffers and amplifies the incoming signal and applies it via C3 to the peak detector, consisting of D2 and C4. It is also....
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This circuit shows a simple way to add text information to a composite-video signal that might be floating at some indeterminate de level. The text generator and composite-video source must have the same sync signal. The video-input and -output signals....
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This high-performance video-camera link transmits signals from your video camera to your VCR, or from your VCR to TVs throughout your home. The first stage of the rf chain is a crystal-controlled oscillator, Q1, with a frequency of 60 to 65 MHz, which is....
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The circuit will accept a video signal, separate the sync pulses, invert the video, and add new video to the old sync pulses. The video signal is brought in through Jl and applied to a clamping circuit consisting of Cl, Dl, D2,D3, Rl, and R2. The clamp....
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The main requirement for efficient de restoration is to provide a short time-constant during the clamp period, with a long time-constantlluring the active line time. The switch within the Harris HI201HS has an on resistance of 30 0 and the PM! buffer,....
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The circuit uses a track-and-hold amplifier in a closed-loop configuration to clamp the back-porch voltage of a standard video waveform to 0 V. The circuit"s outputs include a clamped composite-video signal and a TTL-level horizontal-blanking pulse.....
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Tum on a game, computer, videodisc player, or whatever, and its output takes priority over the antenna-derived signal-the antenna is disconnected and the alternate source is fed to the monitor. When the alternate video source is no longer detected, the....
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This figure shows a one-of-two switch with a sunnning amplifier. The video source"s line can be terminated either externally or internally to switch RO. With this termination resistor, a load change of less than 1 0 will be seen by the source when the....
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This circuit uses a sync-generator chip, a counter, and a decoder to detect the horizontal sync pulse that occurs a..
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IC5 generates RS-170 NTSC synch. IC1, IC2, and IC3 make up the red, green, and blue video signals that drive the video ..
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The A/B Switch circuit consists of three ICs and a handful of resistors. Two gates from a 4011 quad 2-input N..
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In the video system of Figs. A and R, a single coaxial cable carries power to the remote location, selects one of eight video channels, and returns the selected signal. The system can choose one of several remote surveillance-camera signals, for example,....
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This unit picks up your ATV signal by sampling the transmission line with negligible insertion loss. It uses 2 N connectors for input and output connections. A BNC connector is used on the video output. The detected output is connected to your monitor and....
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This combination sync stripper and universal video interface can solve a lot of problems for you, including Super-Nintcndo-to-anything interfacing, video overlay and scope TV frame locking. Kits, fully tested units, and custom cable assemblies are available....
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The video master consists of a series of converters that place all your video sources on unused UHF channels, which then combines them with normal TV channels (terrestrial or cable into one cable). That one cable can then feed several TV sets for....
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This project is influenced by the effort to achieve a security system that can be used in the business, or even very simply at the door of your home. This security system uses the microcontroller of the Arduino Uno system in combination with RFID (radio....
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Once the circuit gets current, all variables are initialized and the loop function is continually running. Initially all LEDs are off and there is no signal at the output. By pressing the signal switch, the first light that shows the most signal is at the....
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This inverter uses no special components such as the torodial transformer used in many inverters. Cost is kept low with the use of cheap, readily available components. Essentially, it is a power amplifier driven by an asta-ble multivibrator. The frequency is....
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The circuit is capable of providing power for portable Geiger counters, dosimeter chargers, high resistance meters, etc. The 555 timer IC is used in its multivibrator mode, the frequency adjusted to optimize the transformer characteristics. When the output....
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Low power dc to dc converter obtained by adding a flyback circuit to a square wave oscillator. Operating frequency is 20 kHz to minimize the size of LI and C2. Regulation is achieved by zener diode D2..
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Push-pull outputs are used in this transformer-coupled dc-dc regulating converter. Note that the oscillator must be set at twice the desired output frequency as the SGI 524"s internal flip-flop divides the frequency by 2 as it switches the PWM signal from....
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A low-current flyback converter is used here to generate ±15 volts at 20 mA from a +5 volt regulated line. The reference generator in the SG1524 is unused with the input voltage providing the reference..
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Capacitor C5 and potentiometer R12 determine the frequency of the output signal at pin 3 of IC1, the 555 oscillator. The output signal is differentiated by C3 and C4 before it"s input to the base of power transistors Q1 and Q2 via diodes D1 and D2,....
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In this circuit, a CMOS inverter, such as the CD4069, is used to convert the open drain Lx output to a signal suitable for driving the gate of an external P MOSFET. The MTP8P03 has a gate threshold voltage of 2.0 V to 4.5 V, so it will have a relatively....
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This low-power inverter uses only 9 parts and turns 10 to 16 Vdc into 60-Hz, 115-V square-wave power to operate ac equipment up to 25 W. The first section of the 556 timer chip is wired as an astable oscillator with R2 and C1 setting the frequency. The....
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A 555 timer (IC1) generates a 120-Hz signal that is fed to a CD4013BE flip-flop (ICl-a), which divides the input frequency by two to generate a 60-Hz clocking frequency for the FET array (Ql through Q6). ..
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This dc-to-ac inverter is based on the popular 555. A 555 oscillator circuit drives a buffer amplifier consisting of Ql, Q2, and Q3. The circuit operates at 150 to 160 Hz. Tl can be a 6.3-V or 12.6-V filament transformer as applicable...
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U1 is a 4060 12-stage binary ripple counter that is used as a free-running oscillator; its frequency of oscillation is: 1/2.2 CIR2. The output of U1 is applied to U2, a 14-stage binary ripple counter that provides square-wave outputs of lfz, 1/4, "is, and....
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In the 556 timer, the timing is a function of the charging rate of the external capacitor. For long time delays, expensive capacitors with extremely low leakage are required. The practicality of the components involved limits the time between pulses to....
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The unit provides a square-wave output that is rich in harmonic content. The circuit"s output frequency can be varied from 50 Hz to 15 kHz. The heart of the circuit is a 555 astable connected in its equal mark/space mode. The frequency is controlled by....
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The alarm circuit has a single 555 oscillator/timer (Ul) performing double duty; serving both in the alarm-trigger circuit arid the entry- delay circuit. In this application, the trigger input of IJ1 at pin 2 is held high via Rl. A normally-closed sensor....
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Circuit for applying a dc-coupled FM or PPM to a 555 configured as an oscillator. IC-1 - Motorola MC-1374P. IC-2 - National LH0002C. L1, L2 - Mouser Electronics #421IF200. C1. C2 - Silver mica, 300 pF. All 0.1 uF cap., ceramic disc, 16V. C3 - 100 uF, 10 V,....
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This relatively simple, inexpensive circuit requiring one trimming operation can multiply or divide with a consistentaccuracy of greater than 1 part in 1,000. An inexpensive CMOS version of standard 555 timer chip T, in conjunction with low-drift LMll....
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This is a Tesla/joule thief hybrid circuit that its inventor claim to produce 90 times the input power! The circuit can be self looped and can provide 1050W of power. from the 1050W only the 11.6W will loop back to supply the joule thief. If you remove the....
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This Jammer circuit can be used indoor or outdoor and the coverage/range that offers is about 30 meters in order to disconnect the wireless devices from their communication with the base station. In the circuit design, we use the frequency ranges reserved by....
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** UPDATED 2014 ** This project is the original High power mobile phone Jammer circuit, and all updates are posted here. All other versions are just copied from next.gr. First off all you should be very careful how to use this device. Its fully illegal and....
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A quad op amp can simultaneously generate four synchronized waveforms. The two comparators (Al and A3) produce square and pulse waves, while the tWo integrators (A2 and A4) give triangular and sawtooth waves.
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The scheme presented delivers waveforms from any function generator producing a triangular output and a synchronized TTL square wave. A1 and A2 act as a two-phase current fectifier by inverting the negative voltage appearing at the input of Al. Positive....
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An oscillator/amplifier is resistively tunable over a wide frequency range. Feedback circuits containing operational amplifiers, resistors, and capacitors synthesize the electrical effects of an inductance and capacitance in parallel between the input....
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A circuit for multiplying the width of incoming pulses by a factor greater or less than unity is simple to build and has the feature that the multiplying factor can be selected by adjusting one potentiometer only. The multiplying factor is determined by....
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The circuit is designed around the Intersil 8038CC. Frequency range is approximately 20 Hz to 20 kHz—a tuning range of 1000:1 with a single control. The output frequency depends on the value of C2 and on the setting of potentiometer Rl. Other values of C2....
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The positive and negative peak amplitude is controllable to an accuracy of about ± 0.01 V by a dc input. Also, the output frequency and symmetry are easily adjustable. The oscillator consists of an integrator and two comparators—one comparator sets the....
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A variable oscillator covers 3.2 to 22 MHz in two bands—providing coverage of 80 through 15 meters plus most crystal-filter frequencies. Optional 455 kHz and 10.7 MHz crystal oscillators can be switched on-line for precise if alignment. Generator output is....
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The circuit consists of a variable current source that charges a capacitor, which is rapidly discharged by a Schmitt-trigger comparator. The sawtooth waveform thus produced is fed to another comparator, one with a variable switching level. The output from....
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The Colpitis sinusoidal oscillator provides stable output amplitude and frequency from 0°F to +150°F. In addition, output amplitude is large and harmonic distortion is low. Oscillation is sustained by feedback from the collector tank circuit to the....
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The pulse repetition rate is selected by positioning SI to the desired position and the rate remains essentially constant when the resistors which determine on-period and off-period are adjusted.
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A Wien bridge oscillator produces sine waves with very low distortion level. The Wien bridge oscillator produces zero phase shift at only one frequency (f = Vx t RC) which will be the oscillation frequency. Stable oscillation can occur only if the loop gain....
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Transistor Q5 and the 1000 ohm resistor form the variable element needed for controlling the frequency of VCO by limiting the charging current flowing into the 0.15 timing capacitor according to the forward bias being applied to Q5. As the voltage on pins 2....
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The circuit uses two gates of a 7400 IC cross-connected to form an astable multivibrator driven by the 1-pulse per second output of the digital clock IC. The hee-haw circuit has a low frequency astable modulator added to make a self-contained European-type....
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Using a single chip LM324 can, with active R-C networks, reduce the size of a 3-phase waveform generator, and prove useful in compact and stable 3-phase inverters. One quarter of an LM324 is used as a Wien bridge oscillator generating a pure sinusoidal....
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This circuit works well in the range of 50 kHz to 500 kHz. Slight component modifications are needed for higher frequency operation..
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If the output is low, application of a negative-going pulse to the trigger input sets the flip-flop (Q goes low), drives the output high, and turns off 1. Capacitor C is then charged through Ra until the voltage across the capacitor reaches the threshold....
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This circuit has a Schmitt trigger and integrator built around one op amp. Timing is controlled by the RC network. Voltage at the inverting input follows the RC charging exponential within the upper and lower hysteresis levels. By closing the switch SWI, the....
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This low-cost operational-amplifier circuit (A) generates four different functions with adjustable periods. For the components shown here, the period of the output waveforms is given by T = 4RC and T = 2RC. With switch SI in position A, VI is a triangular....
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To obtain a 1000:1 Sweep Range, the voltage across external resistors Ra and Rb must decrease to nearly zero. This requires that the highest voltage on control pin 8 exceed the voltage at the top of Ra and Rb by a few hundred millivolts. The circuit achieves....
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The output-pulse width from the circuit is a linear function of the input pulse"s height. You can set the circuit"s input threshold to discriminate against low-level pulses, while fixed components limit the circuit"s maximum output -pulse width. With a....