Top Circuits Page 2
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The gain of the low-cost IC is internally fixed so that it is not less than 34 dB (50 times). A unique input stage allows input signals to be referenced to ground. The output is automatically self centering to one half the supply voltage. The output is also....
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The circuit is a preamplifier with digital regulation intensity of sound. He is separated in three departments. In first schematic (Fig.1), is found the circuit of control of electronic potesometer. The control become from two pressing switches. The S1 (UP),....
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A preamp designed for the minimalist, and having no frills at all is the design goal for this project. It is designed as a preamp for the Death of Zen (DoZ) Class-A power amp (Project 36), and has very low levels of noise and distortion, in a minimum....
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In this circuit exists a second designing proposal of preamplifier RIAA. The first stage uses discernible components and in second exist a opamp. [IC1]. In the negative feedback exist the correction RIAA filters. Certain points need certain discriminators:....
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The preamplifier that appears in the figure is a completely symmetrical preamplifier, from the input as the exit and it works in Class A. It does not have somebody innovation, simply it uses good solutions, in order the result is what should. Such proposal....
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Another one unit of graphic EQ. five bands. The basic difference with the other circuits is, that I use instead of IC, transistor and the power supply, go up in +/- 24V DC, ensuring low distortion and bigger margins of overloading. With switch S1, we can....
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The volume control in a hi-fi amp or preamp (or any other audio device, for that matter), is a truly simple concept, right? Wrong. In order to get a smooth increase in level, the potentiometer (pot) must be logarithmic to match the non-linear characteristics....
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Audio graphic equalizers are very common as commercial products (for Hi-fi, car audio and stage use) but circuits for them are very rarely published. I didn`t design this one but it`s really very simple. The details shown are for a 7 band but the principle....
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The circuit of graphic equalizer, allocates ten adjusting potesometer , that each one from them affects in a predetermined area of frequencies, the central frequency of which abstains a octave (double), from the central frequencies of her neighbouring....
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The circuit constitutes a natural extension of Mic-Line balance unit, but can be adapted to any other audio circuit. It is made up of two units in the series : A) A classic unit bass/ Treble and B) a parametric unit of mid frequencies. Both units can also be....
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Ql is connected as an emitter follower in order to present a high input impedance to the guitar. C2, being a relatively low capacitance, cuts out most of the bass, and C3 with RV1 acts as a simple tone control to cut the treble, and hence the amount of....
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The circuit has a frequency response ranging from 100 Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor Rl sets the input impedance to any desired value. Commonly, it will be....
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This broadband amplifier covers the 225-400 MHz military communications band producing 10 watt RF output power and operating from a 28 volt supply. The amplifier can be used as a driver for higher power devices such as 2N6439 and MRF327. The circuit is....
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The operation of the circuit is like an enabled inverter, that is, the output Y = B provided A is high. If A is low, output is low (independent of the state of B). When the signals A and or B1 are connected to the inputs A and of this gate the output Y is....
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A clever charger circuit that safely can charge any Ni-Cd battery. Offers charge current sellection, polarization detection and protection and the ability to connect many batterys in siries. Ni-Cd bateries can be recharged more than 1000 times before become....
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Rectified and filtered voltage from the 24 Vac transformer is applied to the LM723 voltage regulator and the npn pass transistor set up for constant current supply. The 470 ohm resistor limits trickle current until the momentary pushbutton (S2) is depressed,....
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The charger is based on a charging voltage of 2.4 V per cell, in accordance with most manufacturers' recommendations. The circuit pulses the battery under charge with 14.4 V (6 cells ? 2.4 V per cell) at a rate of 120 Hz. The design provides current limiting....
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An LM317 voltage regulator is configured as a constant-current source. It is used to supply the 50 mA charging current to S01-S06, an array of AA-cell battery holders. Each of the battery holders is wired in series with an LED and its associated shunt....
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Operation amplifier A1 directly drives the VN64GA with the error signal to control the output voltage. Peak rectifier Dl, CI supplies error amplifier A1 and the reference zener. This extra drive voltage must exceed its source voltage by several volts for the....
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The circuit provides a simple and cost-effective solution to matching resistors and capacitors. Impedances ZR and Zx form a half-bridge, while OSC and OSC excite the bridge differentially. The external op amp is a FET input amplifier (LF356) with very low....
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The transistor is connected as an audio oscillator, using an audio transformer in the collector. The secondary goes to a linear pot...
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A silicon-controlled rectifier is installed in parallel with the 12-V line and connected to a normally-closed 12-V relay, K1. The SCR's gate circuit is used to sample the applied voltage. As long as the applied voltage stays below a given value, SCR1 remains....
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The design delivers a regulated 400-V, 60-W output. The TL494 switching regulator governs the operating frequency and regulates output voltage. Rl and Cl determine switching frequency, which is approximately 0.SRC—100 kHz for the values shown. The TL494....
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This circuit uses a tricolor LED display to indicate acceptable and unacceptable output voltages. One to set the upper voltage limit, the other, the lower voltage limit. When the monitored voltage is above the set maximum, the LED display turns red. Yellow....
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The circuit monitors the input to the microprocessor 5 V regulated supply for voltage drops and initiates a reset sequence before supply regulation is lost. In operation, the resistor capacitor combination Rs and Cj form a short time constant smoothing....
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To generate regulated ± 5-V supplies from a pair of dry batteries, the circuit of Fig. 1 is commonly used. In order to give protection from inadvertent reverse connection of a battery, a diode in series with each battery would produce an unacceptable....
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The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2.
Separately, a tunable (R12) single frequency is produced by the LM567 oscillator U1. The LM567 is a tone decoder but here its input is....
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Basic operation of the monitor attached to the circuit is to detect objects (obstacles), at distances ranging from a few millimeters to and a few centimeters. Depending circuits used in industry and hospitals. The position sensor IC2 optoapomonotis used a....
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Assume the correct phase sequence to be VA-VB-VC. The circuit terminals are connected such that Tl gets connected to phase A and T2 to phase B. The capacitor advances the voltage developed across R2 due to phase "B" by — 60°, while the voltages developed....
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This circuit prevents damage to the load due to incorrect phasing. The three power SSR's are only permitted to turn-on for a phase sequence of phase A leading phase B. If phase A lags phase the input currents will cancel, causing the SCR and the inhibit SSR....
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ICla and IClb are wired as a slow astable multivibrator and IClc-ICld are wired as a fast astable. The output of the slow astable modulates the frequency of the fast astable, and the output of the fast astable is fed to the external speaker via the Ql VMOS....
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The circuit uses a thermistor and three sections of a LM3900 quad op amp IC. When the temperature drops to 36°F the LED indicator flashes about once each second. The flashing rate increases as temperature drops to 32°F when the LED remains on. Amplifier I....
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This circuit switches car headlights to the low beam state when it senses the lights of an on-coming car. The received light is very low level and highly directional, indicating the use of a lens with the detector. A relatively large amount of hysteresis is....
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The continuity tester is for tracing wiring on printed circuit boards. It only consumes any appreciable power when the test leads are shorted, so no On/Off switch is used or required. The applied voltage at the test terminals is insufficient to turn on....
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The tachometer, on the same shaft as the dc motor, is simply a generator. It gives a dc output voltage proportional to the speed of the motor. A summing amplifier, Al, controls its output so that the tachometer voltage equals the input voltage, but of....
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The solar cell is connected across the input of the FET (field-effect transistor), Ql, so that it will produce positive dc voltage to the gate when activated by light shining through the open shutter, decreasing the negative gate-source bias already....
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This tester is for tracing wiring on Printed Circuit Boards. Resistors below 50 ohms act as a short circuit; above 100 ohms as an open circuit. The circuit is a simple multivibrator switched on by transistor T3. The components in the base of T3 are Dl, Rl,....
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The circuit can be used in telephone lines for speech activity detection purposes. This detection is very useful in the case of half-duplex conversation between two stations, in the case of simultaneous transmission of voice and data over the same pair of....
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In the absence of radiation, no current is drawn. At normal background radiation levels the power consumption is extremely low. The instrument may be left on for several months without changing batteries. In this way the detector is always ready to indicate....
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A Coil Coupled Operation Metal Detector made from readily obtainable components and using an ordinary medium receiver as a detector. The metal detector shown here may well represent a new genre. At any rate, after some exposure, it is regarded as such by....
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This circuit uses a 15-kHz oscillator coil. Whan metal placed ixi the energy field is withdrawn, the oscillator voltage is rectified and compared to a reference. A drop in oscillator voltage therefore operates comparator IC2 and D4 (LED) extinguishes.
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A bridge rectifier and 12-volt regulator powers the MOSFET sensing circuit. The unregulated output of the bridge rectifier operates the drain solenoid via switch SI. The sensor itself is built from two electrodes, one made of copper, the other of lead. In....
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While the battery is being charged, its voltage is measured at V. If the measured voltage is lower than the minimum the relay will be energized, that wiU connect the charger circuit. When the battery voltage runs over the maximum set point, the relay is....
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When the lights of an on-coming car are sensed by photo-transistor Ql, things get going. Sensitivity is set by the 22-megohm resistor, R5, to about half a foot-candle. The relay used has a 12-volt, 0.3A coil.
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This flasher operates from a 12-volt car or boat battery. It offers 36 to 40-watts output, variable flash rate (up to 60 flashes per minute), independent control of both on and off cycles and photoelectric night and day control that turns the flasher on at....
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This circuit uses a set of 13 differently colored LEDs to generate a full color spectrum. The photo does not fully represent the colors generated due to camera limitations. The real-world display is very eye-catching. If you want to "trick out" your PC, this....
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The circuit will modulate the light from the LED using a crystal microphone or a loudspeaker output. To obtain the maximum range, the optical system must be efficient (see example). Either a convex lens or a concave mirror can be used to convert the LED....
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The oscillator delivers an output of high spectral purity without any substantial sacrifice of the usual stability of a crystal oscillator. The crystal in addition to determining the oscillator's frequency, is used also as a low-pass filter for the unwanted....
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For maximum range, the receiver must be designed in the same manner as a radio receiver front end, since the received signals will be similar in both frequency component and in amplitude of the photodiode current. The major constraint on the receiver....
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The generator described here is intended for multiburst signal square waveform generation and can be used as a device for characterizing the response of TV monitor amplifiers as shown. The circuit is an RC oscillator with NAND gates (IC4-4011), with its....
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The circuit provides three square wave outputs with 120° of phase difference between each other. Reference clock frequency is twice that of the required frequency. This can be obtained from a crystal oscillator with a chain of dividers or by using LM 555 in....
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In the circuit in Fig. 1, ICla produces the integral term required but also has the side effect of producing a proportional term not required, so this term is subtracted by IClb leaving a pure integral. If the ratio R2/R5 does not exactly match the ratio of....
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A lot of friends me asked to draw a more shrunk circuit 2-ch mixer, which will contain also, operation CROSSFADER. The circuits can be modified and added also other channels, repeating basic that I give. It can are added channels stereo PHONO/line or even....
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The first circuit energizes the relay when the temperature rises above the preset level. The second circuit energizes the relay when the temperature falls below the preset level. The two circuits are practically identical. The only difference between them is....
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The relay operates a certain time, td, after power is applied to it, and then it operates for a length of time, tc. The SCR fires when the voltage on Ci reaches VA. This operates the relay, which stays activated until the current charging C2 drops below the....
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This circuit accepts bipolar control inputs of ± 5 V and provides a phase-chopped output to a dc load (such as a servo motor) of the same polarity as the input. The rms voltage of the output is closely proportional to the control input voltage. N-channel....
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Pushing the button once will energize the relay. Pushing the same button a second time will de-energize the relay. Any simple momentary action push-to-make switch will do...
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An AC triggered switch for low frequency signals. This is a basic ac voltage operated switch made from discrete components. Both Q1 and Q2 work as common emitter amplifiers, but the biasing of Q1 is arranged by R3 and R4 so that about 0.5V is applied to its....
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This circuit is a static SCR switch for use in a dc circuit. When a low power signal is applied to the gate of SCR1, this SCR is triggered and voltage is applied to the load. The right hand plate of C charges positively with respect to the left hand plate....
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This circuit uses a low-cost feedback scheme in which the dc voltage developed from the primary-side control winding is sensed by the UC1842 error amplifier. Load regulation is therefore dependent on the jcoupling between secondary and control windings, and....
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A light dimmer, a 1 µf capacitor and a 12 V car ignition coil form the simple line powered HV generator. The current in the dimmer is shown in Fig. B. At times tp t2, set by the dimmer switch, the inner triac of the dimmer switches on, and a very high and....
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A 6 V battery can provide 100-150 Vdc center-tapped at a high internal impedance (not dangerous though it can inflict an unpleasant jolt). A 6.3 V transformer is connected ' 'in reverse'' with a transistor used in a Hartley oscillator configuration. The....
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Everytime the push-to-talk button is closed the light will go on. The antenna samples the output RF from the transmitter. That signal is then rectified (detected) by germanium diode Dl, and used to charge capacitor C2. The dc output is used to trigger a....
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A simple voltage-to-current converter is shown in the figure. The current out is 0t or Vjn/R. For negative currents, a pnp can be used and, for better accuracy, a Darlington pah-can be substituted for the transistor. With careful design, this circuit can be....
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Conversion of triangle wave shapes to sinusoids is usually accomplished by diode-resistor shaping networks, which accurately reconstruct the sine wave segment by segment. Two simpler and less costly methods may be used to shape the triangle waveform of the....
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This circuit can generate a European police-car siren, bird noises, spaceship sounds, etc. In addition, it can be put to use as a doorbell, an alarm, etc. The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output....
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This circuit consists of twin-T sine-wave oscillators. Each oscillator has a filter in the feedback loop. If the loop gain is greater than unity, the circuit will oscillate. Gain is adjusted to be just less than unity. Touching the touch plate starts the....
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The waveform of a steam whistle is a complex combination of white noise and an audio frequency oscillation. The noise generator is a transistor (Ql) biased into zener mode. The audio frequency oscillation is a straightforward mixture of two similar (but not....
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The CD4069 or 74C04 hex inverter—is used as^ fixed-frequency oscillator centered around 100 kHz. U2 contains the variable frequency oscillator and balanced modulator. The CD4046 is a phase-locked loop and R3, R4, and C2 determine the center frequency of....
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In those cases we want to measure the temperature in an area far from where it is. The imaging unit installed, you should find some way to connect the latter with the necessary sensor. The cables we use most often will have three two conductors for power....
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This circuit provides on/off switching, soft starting, current monitoring, current tripping, and protection against overcurrent for a 30 Vdc power supply at normal load currents up to 2 A. The switch is turned on by an "on" command pulse; it is turned off by....
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This buck-derived circuit provides up to 8 A at 5 Vdc operating off 24 to 32 Vdc. The two power MOSFETs in the circuit conduct alternately for equal periods. Switching frequency is 150 kHz, set by the PWM125 controller. Output of the two MOSFETs is....
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An opto-interrupter made with Lego beams, regular parts, a 6 hole pulley wheel and an axle...
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The input signal is applied through R3 to the inverting input of the summing amplifier and the output is taken from the first integrator. The summing amplifier will maintain equal voltage at the inverting and non-inverting inputs. Defining 1/R1C1 as 1 and....
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With the circuit shown here the response at one octave off tune is within 10% of the far out response: notch sharpness may be increased or reduced by reducing or increasing.respectively the 68 ohm resistor. Linearity tracking of R8 and R9 has no effect on....
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This simple AM circuit uses a 561B. There's no inductance/capacitance tuning circuit. The 365 pF capacitor connected between pins 2 and 3 does all the tuning. The circuit needs a good outside antenna and a solid ground. And if you want to further improve....
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This circuit was designed for testing fuel cells, but it could also be used for testing batteries under a constant current load. It provides a dynamic, constant current load, eliminating the need to manually adjust the load to maintain a constant load. For....
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Continually monitors battery voltage during use and consumes only about 250 ? A (until the end point is reached). Near the end point Trl turns off, allowing Tr2 to illuminate the LED to increase current drain further leading to a distinct turn off point...
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This circuit gives an early warning of the discharge of batteries. Zener diode Dl is chosen for the voltage below which an indication is required (9 V). Should the supply drop to below 7 V, Dl will cease conducting causing Ql to shut off...
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The circuit is built around a 4001 quad two-input NOR gate, it provides switch selectable auto-advance times of 5, 10, 15, 20, 25 or 30 seconds through the remote-control socket of your projector. Ula and Ulb form an astable multivibrator, with its operating....
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The Wireless Keylogger consists of two main building blocks: the transmitter, and the receiver. The actual keylogging takes place in the transmitter, which is in fact a PS/2 hardware keylogger, with a built-in 2.4 GHz wireless module. Captured keystroke data....
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This free-running multivibrator uses an external current sink to discharge the timing capacitor, C. Therefore, interval ^ may easily be 1000 the pulse duration, t1( which defines a positive output. Capacitor voltage, V^, is a negative going ramp with....
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A JFET (Ql) serves as the oscillator. D2 helps to stabilize the transistor by limiting positive sinewave peaks and stabilizing the bias. Output from Ql is supplied to a class A buffer, Q2. It operates as a broadband amplifier by means of Tl, which is....
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This oscillator uses standard inverters, one resistor and one capacitor, and has no minimum operating frequency. R and C must be chosen such that currents into the gates are below recommended operating limits and that leakage current into the gates and into....
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Flashing occurs each time the capacitor discharges through the tumed-on SCR. When the discharge current falls below the SCR holding current, the SCR turns off, and the capacitor begins charging for another cycle. ..
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A pair of non-zenered MOSPOWER transistors, a pair of LEDs and a simple RC circuit make an easy sequential flasher with almost "unlimited sequencing time—from momentary to several seconds. The infinite input resistance of the MOSFET gate allows for very....
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A 555 timer IC, operating in the one-shot mode, is triggered by light striking photoresistors. These normally have a resistance of several megohms but, in the presence of light, that resistance drops to several hundred ohms, permitting current from the....
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C1 = 3 750 pF 500 V silver-mica capacitor. C2= 100 pF preset capacitor (Jackson C803). C3 = 75 pF variable capacit..
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This antenna might help to reduce power-line noise. A plastic hula hoop or conduit 3 feet in diameter, covered with aluminum foil as a shield is used for LI and L2. LI is two turns and L2 is one turn, threaded through the loop. SI selects 160- or 80-m....
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This preamplifier has a built-in regeneration control boost gain selectivity. CI is a single or multi-gang AM broadcast-band tuning capacitor. LI is a ferrite loop antenna, tapped at about 15 to 25% of total turns. This circuit should prove useful for....
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All capacitors in this circuit are disc ceramic. Fixed-value resistors are 1/.-or 1/2-W carbon. Rl controls the gain of Ul. RFCl is a miniature 2.5mH rf choke. ..
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The signal booster, built around a few transistors and support components, offers an RF gain of about 12 to 18 dB ..
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This circuit is designed to make a short pull-up antenna perform like a long wire antenna, while offering no voltage gain...
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A J309 Siliconix FET feeds a 2N5109 in a wideband RF amplifier configuration. A relay is used to bypass the amp..
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Time IO-bit conversion is 3.3 MHz with a p 3. Clock. This converter uses an approximation 2504 12-bit register in successive operating mode where the short-cycle end signal conversion is taken from the first bit used in the SAR (QLO)...
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A bipolar input, high speed A/D converter uses two AM25L03s to form a 14-bit successive approximation register. The comparator is a two-stage circuit with an HA2605 front-end amplifier used to reduce settling time problems at the summing node..
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The CMOS comparator in the successive-approximation system determines each bit by examining tbe charge on a series of binary-weighted capacitors. In tbe first phase of tbe conversion process, the analog input is sampled by closing switch SC and all ST....
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The analog input is fed into the span resistor of a DAC. The analog input voltage range is selectable in the same way as the output voltage range of the DAC. The net current flow through the ladder termination resistance; i.e., 2 KO for HI-562A; produces....
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Conversion speed of this design is the sum of the delay through the comparator and the decoding gates. Reference voltages for each bit are developed from a precision resistor ladder network. Values of R and 2R are chosen so that the threshold is 1/z of the....
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An aid conversion technique which combines some of the speed advantages of flash conversion with the circuitry savings of successive approximation is termed half-flash. In an 8-bit, half-flash converter, two 4-bit flash aid sections are combined. The upper....