Top Circuits Page 15
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Transistors Ql and Q2 and their associated components provide: a low-impedance output with the necessary power to drive the output stages, give increased gain tohigh frequencies, and peaking the video for enhanced transient response. Emitter followers Q3,....
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Q1 and Q2 form a differential stage which single- ends into the LT1010. The capacitively terminated feedback divider gives the circuit a de gain of 1, while allowing ac gains up to 10. Using a 20-fl bias resistor, the circuit delivers 1 V pk-pk into a....
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This circuit is a traditional summing amplifier configuration with the addition of the de clamping circuit. The operation is quite simple; each component-synchronization, color burst, picture information, etc.of the composite video signal is applied to its....
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This amplifier employs a cascaded op amp integrator and transistor buffer, Q1, to drive the gain control element. Except for a simple modification, the HA-5190/5195 stage is connected as a conventional noninverting op amp, and includes input and output....
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This configuration utilizes the wide bandwidth aod speed of HA-2540. plus the output capability of HA5033. Stabilization circuitry is avoided by operating HA-2540 at a closed loop gain of 10, while maintaining an overall block gain of unity. A maximum....
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This buffer amplifier"s overall harmonic dis tortion is a low 0.01 % or less at 3-V rms output into a 500-fl load with no overall feedback. The LT1010CT offers a 100 V/p.s slew rate, a 20 MHz video bandwidth, and 100 mA of output. A pair of JFETs, ]1....
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Ail ultrasonic cleaner is useful to clean certain items. This circuit uses a microcontroller to control timing and give a digital readout, but only the basic oscillator can be used, if desired. RESL, RES2 are piezoelectric transducers driven by power....
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The circuit has a typical voltage gain of 84 dB and a typical AGC range of 80 dB. It gives very small changes in bandpass shape, usually less than 1 dB tilt for 60 dB compression. There are no shielded sections. The detector uses a single tuned circuit (L3....
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This circuit does not require an output transformer or an output coupling capacitor; the annunciator can easily be turned on or off by a control input voltage driving a 10Mohm input resistor, R3. For a smaller acoustic output, replace output transistor Ql,....
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Put the car in reverse and the circuit provides a loud, audible beep at the rate of about one per second (1Hz). Half of U1, a 556 dual oscillator/timer, is used as a slow-pulse oscillator with a rate of about 1Hz. Components R2, R1, and C1 form the long time....
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This circuit uses a CA5422 dual BiMOS microprocessor op amp. The bootstrap amplifiers minimize bias currents while maintaining electrostatic discharge protection. ..
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A self-interrupting device connected to a voltage source functions as a switch that repeatedly open..
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When the vehicle"s backup lights kick on, or when the manual switch (SI) is closed, a small current is fed to the base of Ql...
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This circuit will generate an ear-splitting 110 dB from 9 V. The setup uses a single 74C14 (CD40106B) CMOS hex inverting Schmitt-trigger IC, wliich must be used with a piezoelectric device with a feedback terminal. The feedback terminal is attached to a....
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A complete zero-voltage switch solid-state relay contains an input circuit, an output circuit, and the power thyristor. The circuit illustrates a triac power thyristor with snubber circuit and GE-MOVRII Vans tor transient over-voltage protection. The 22 ohm....
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This circuit can be used to prevent relay contact arcing for loads up to 50 amperes. There is some delay between the time a relay coil is energized and the time the contacts close. There is also a delay between the time the coil is de-energized and the time....
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Capacitor Cl and body capacitance (C2>of the operator form the voltage divider from the hot side of the ac line to ground. The voltage across Cl is determined by the ratio of Cl to C2. The higher voltage is developed across the smaller capacitor. When no one....
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Ql and Q2 are general purpose transistors. The 10 K input pot is adjusted to a point just short of where Ql turns on as indicated by K pulling in. K is any 5 V reed relay. With the values shown for R (100 K) and C (47 µf), timing values from 5 to slightly....
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This circuit modulates a light beam with voice or music from the output of an amplifier. If the 10 K pot is adjusted to slightly less than the Vbe of the transistor, the circuit forms a peak detector..
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This is an on-off control with isolated, low voltage input. Since the switching action is very rapid, compared with the response time of the lamp and the response of the eye, the effect produced with audio input is similar to a proportional control circuit..
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The device remains dormat (in an off condition) until some sound causes it to tum on. The input stage is a 741 operational amplifier connected as a noninverting follower audio amplifier. Gain is approximately 100. To increase gain raise the value of R2..
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This circuit operates a relay each time a sound of sufficient intensity is made, thus one clap of the hands will switch it one way, a second clap will revert the circuit to the original condition. Q2 and Q3 form a Schmitt trigger. The JK flip-flop isoised as....
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The phototransistor and photodarlington couplers act as de relays in saturated switching at currents up to 5 mA and 50 mA, respectively. When higher currents or higher voltage capabilities are required, additional devices are required to buffer or amplify....
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The HllC supplies the de latching relay function and reverse polarity blocking, for currents up to 300 mA, depending on ambient temperature. For de use, the gate cathode resistor can be supplemented by a capacitor to minimize transient and dV/dt....
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When zero voltage switching is not required, methods of providing this function are illustrated. The lowest parts count version of a solid-state relay is an optoisolator, the triac driver HlU. Unfortunately, the ability of the Hll} to drive a load on a....
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In the case where analog signals are being used as the logic control, hysteresis from a Schmitt-trigger input can be used to prevent haH-wave power output. The circuit operation is as follows: at low input voltages, Q1 is biased in the off state. Q2....
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IR radiation from LED2 (modulated by a 1-kHz wave) is keyed by Ul, and Ql is radiated. Reflected IR energy i..
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Tl is tuned to converter-output frequency Ul to provide 45-to-50-dB gain, depending on the design of Tl and T2. C2, C..
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The op amp is wired as a 2 noninverting dc amplifier with a gain that is determined by the R3/R2 ratio. The inp..
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Latching is obtained by storing the gate trigger energy from the preceding half cycle in the capacitors. Powe..
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A monostable relay has two states: operative when a large enough current flows through its coil and quiesc..
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A power MOSFET and a quad exclusive-OR oscillator makes an effective solid-state relay. Figure 75-5(a)"s capacitively iso..
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This simple circuit provides a solid-state equivalent of the electromechanical latching relay (see the figure). What`s more, the switching is clean, highly resistant to vibration and shock, and isn`t sensitive to magnetic fields or position. The circuit....
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Using a 4060 CMOS binary divider and built-in clock oscillator, a long-duration timer can be made veiy simply. The solid-state relay can be sized for your application, and can be replaced with a mechanical relay if a suitable power supply is available. With....
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A sensor turns on Ql to activate the low-frequency 555 oscillator, which pulses LAMP II. Sensor may be sensitive to changes in light or temperature. Either RA or RB can be sensors, as desired. A decrease in RB or an increase in RA will cause the NE555 to....
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When SI is depressed, an initial positive voltage is placed on C2 and the noninverting terminal of Ul. The circuit o..
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When the pushbuttons at either door are depressed, this circuit generates a different tone for each door. Tones are ge..
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This circuit uses only one IC, produces a pleasant tone, and sports a single control for adjusting the tone"s chiming rat..
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When the doorbell switch is pressed, the two monostable stages are activated in sequence, applying bias to a pair of voltage-controlled resistor stages. These then modulate the outputs from a pair of tone generators. The resulting signals are fed to an....
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It is often desirable for a single doorbell to be operated by two buttons, for instance, one at the front door and the other at the back door. The additional button, S2 in series with the break contact of relay Rel, is connected in parallel with the....
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This encoder uses a single contact per key keyboard and provides all other switching function electronically. The diode between terminals 8 and 15 prevents the output going more than 1 volt negative with respect to the negative supply V-..
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This circuit is intended for use with motors, lamps,heatings etc. Continuously from nearly zero up to maximum capacity (5-95%). Almost lossfree control by means of this impulse control. Nearly total turning moment of motors. The transistior T3 must....
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This circuit controls the level of a tank using a bang-bang controlled electrical pump. The actual level of liquid is measured by a capacitive level-meter. The first inverter performs as a capacitance to frequency converter. It is a Schmitt oscillator and....
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A four thyristor controlled bridge is used for operation in two quadrants of the torque-speed characteristics. In the trigger circuits the usual pulse transformers were replaced by self biased circuits which minimize gate power consumption and increase noise....
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By varying either Rl or R2, the oscillator frequency can be adjusted over a narrow range. The R3/R4 ratio sets the second amplifier's gain to compensate for signal attenuation occurring in the phase shifters. The circuits can be driven from an external....
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The system utilizes the H21A1 and a chopper disc to provide superior speed regulation when the dynamic characteristics of the motor system and the feedback system are matched to provide stability. The tachometer feedback system illustrated was designed....
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A bridge circuit consisting of two SCRs and two silicon rectifiers furnishes full-wave power to the motor. Diodes, D3 and D5, supply dc to the trigger circuit through dropping resistors, Rl. Phase delay of SCR firing is obtained by charging C2 through....
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A shot of direct current will instantly stop any ac power tool motor. Switch Si is a center-off, one side spring return. With Si on, ac will be fed to the motor and the motor will run. To brake the motor, simply press Si down and a quick shot of dc will....
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Simple half-wave motor speed control is effective for use with small universal (ac/dc) motors. Maximum current capability 2 amps RMS. Because speed-dependent feedback is provided, the control gives excellent torque characteristics to the motor, even at low....
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Universal motors and shade d-pole induction motors can be easily controlled with a full-wave Triac speed controller. Q1 combines both the triac and diac trigger diodes in the same case. The motor used for the load must be limited to 6 amperes maximum. Triac....
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Virtually any NPN small signal transistor may be used in place of the BC 108 shown. Likewise any suitable NPN power transistor can be used in place of the 2N3055. The output transistor must be mounted on a suitable heat-sink. Short circuit protection may be....
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The circuit uses a 4011 CMOS NAND gate, a pair of diodes and an NPN power transistor to provide a variable duty-cycle dc source. Adjusting the speed control varies the average voltage applied to the motor. The peak voltage, however, is not changed. This....
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When the time delay expires, SCRl conducts and removes the gate signal from SCR2, which stops the motor. Both the time delay and motor speed are adjustable by potentiometers R2 and R3. If heavier motor loads are anticipated, use the larger C30B SCR in place....
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This circuit operates like the one shown in Fig, 57-4, The only differences are that the field is placed across the rectified supply and the armature is placed in the SCR bridge. Thus the field current is unidirectionali)ut armature current is reversible;....
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The resistor capacitor network R1-R2-C1 provides a ramp-type reference voltage superimposed on top of a dc voltage adjustable with the speed-setting potentiometer R2. This reference voltage appearing at the wiper of R2 is balanced against the residual....
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As the speed of an electric drill is decreased by loading, its torque also drops. A compensating speed control like this one puts the oomph back into the motor. When the drill slows down, a back voltage developed across the motor—in series with the SCR....
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The timed two-voltage circuit can start and run a small de motor or solenoid. The input voltage to the LM317 three-terminal regulator ranges from 5 to 40 V, and the output voltage can range from 2 to 36 V. ..
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The controller circuit can reduce a fan"s noise, power consumption, and wear, particularly in the presence of a low, fluctuating ambient temperature. Mount a temperature sensor in the fan"s airstream, and the circuit will adjust the fan speed as necessary....
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This high-performance switching controller for a low-power de servo motor uses a symmetrical complementary- transistor bridge. The bridge acts as a reversing switch between the motor and a single-ended power supply. Since the transistors operate either....
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This electronic motor-speed control circuit is designed to operate in an electrically noisy environment. The circuit includes an optoelectronic pickup device. whichis placed inside the motor housing to provide a speed feedback signal. The circuit....
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This circuit is particularly applicable to digitally-controlled systems in robotic and X-Y positioning applications. By functioning from the 5-V logic supply, it eliminates additional motor-drive supplies. The tachless feedback saves additional space and....
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When the torque load on the motor increases, its current increases. This current increase is sensed across Rs, and positive feedback is applied to the noninverting terminal of the LH0101, thereby increasing the motor voltage to compensate for the increased....
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The PWM controller uses complementary half-H peripheral drivers SN75603 and SN75604, with totem-pole outputs rated at 40 V and 2.0 A. These drivers effectively place the motor in a full-bridge configuration, which has the ability to provide bidirectional....
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In this proximity detector an NE567 tone decoder provides a signal of about 100 kHz that is fed to one sensor. The senso..
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This circuit is intended as a revolution control for small dc motors as fitted, for instance, in small electric drills (..
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This provides bidirectional speed regulation for small motors and requires no tachometer. The voltage th..
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This circuit monitors the power-line (ac) voltage. When a power failure occurs, on restoration of power, the circuit a..
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The system shown consists of the HA-2542, a small 12-Vdc motor, and a position encoder. During operation, the encode..
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Any dc voltage source in the 2- to 15-V range can be chopped into a unipolar square wave that has a peak amplitude nearly equal to the dc source voltage-with circuit (lightly loaded CMOS will swing within a few millivolts of each rail at low frequencies).....
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A center-tapped 240-V transformer is used with two SCR devices to provide rectified ac (pulsating dc) to MOT1...
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The speed-control switch offers reasonably good control and stability to both ends of its operating range. This circuit uses two SCR devices in a full-wave configuration to control the dc power to a motor. ..
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Dc power can also be controlled via fiberoptics. The circuit provides an insulated speed control path for a small dc actuator motor (< Vn hp). Control logic is a self-contained module requiring about 300 mW at 12 V, which can be battery powered. The control....
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Most standard household appliances and portable hand tools can be adapted to variable -speed operation by use of this simple half-wave SCR phase control. It can be used as the speed control unit for the following typical loads pro-videe they use series....
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The circuit shown here can be used to control the speed and direction of rotation of a series-wound dc motor. Silicon controlled rectifiers Q1-Q4, which are connected in a bridge arrangement, are triggered in diagonal pairs. Which pair is turned on is....
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This circuit uses a tachometer to generate a feedback signal which is compared to a reference supplied by the auxiliary output. When power is applied, the tachometer output is zero and the regulator output comes on, forcing current into the motor. As....
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The NE5561 provides pulse-proportional drive and speed control based on de tachometer feedback. This simple switching circuit consists of transistor 2N4920 pnp with a commutation diode used to deliver programmed pulse energy to the motor. A frequency of....
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The figure illustrates a reversible de motor drive application with adjustable speed control. The D inputs for these drivers are complementary and can be tied together and driven from the same logic control for bidirectional motor drive. The enables are....
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This new circuit uses four chips, with an option of using just three (the flip-flops and AND g..
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Connected in this manner, an LM317 1-A adjustable-voltage regulator can be used to control the speed of a miniature dc motor or vary the brilliance of a small lamp. The circuit does so by controlling the pulse width, and therefore the current, to the load....
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The HI-506 multiplexer is used as an analog input selector, controlled by a binary counter to address the appropr..
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In this circuit, an HA-4900 series comparator is used in conjunction with a D/A converter to form a simple, vers..
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In this circuit, data at input C is amplified by IC2 and then fed to modulator IC1. IC1 g..
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This receiver consists of an input network amplifier IC7 FSK PLL detector ICG, and output am..
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Display interface uses the ICM7218A/B with an 8048 family microcontroller. The 8-bit data bus (DBO/ DB7-IDO/ID7) transfers control and data information to the 7218 display interface on successive WRITE pulses. The mode input pins on the microcontroller.....
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This matrix can show the values of two variables, for example, frequency and voltage. The display is a graph made from a matrix of LEDs. The LEDs on each axis are color coded, red for out of tolerance and green for in, fanning a red band around the inner....
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The use of a switching transistor (like a 2N2222 or 2N3904) allows use of the CD4511B with a common-anode display. should be chosen to provide about 1 mA to drive Ql and Rr should provide enough current to drive the display...
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These two amplifiers are of very good quality, simple and economical in their manufacture. They have two inputs for a 4mV (500KΩ) sensitivity microphone and an input for any 200mV (1MΩ) sound source, that is, the first input is for speech and the second one....
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The output of this modulator consists of two 6AQ5 lamps in a PUSH-PULL arrangement with a maximum output of 15W. 6C4 is used as a reversing lamp. The pre-amplifier role is played by the double-stage ESC83. The potentiometer R1 performs voice volume adjusters....
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The amplifier of this design is 30 Watt and is suitable for microphone-inducing. It accepts a crystalline microphone and can be used for speeches, lectures, as a transmitter modulator and generally where it can be useful as a common frequency amplifier. The....
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The design of the 40W Valve Amplifier is shown in the figure. In valve amplifiers the predominant feature is the strong presence of the second and third harmonics, sometimes in agreement with the fourth and fifth, but always with a much wider width. Higher....
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This simple circuit will energize and de-energize a relay at the push of a button. Any type of momentary action push-to-make switch can be used. Pushing the button once - will energize the relay. And pushing it a second time - will de-energize the relay..
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An op amp is used as a comparator and a sink for LED current. The output voltage of the amplifier changes about 1.4 V depending on the direction of the current. Only one transistor is on at any time. Maximum LED current is limited to 25 mA by overcurrent....
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Input 1 is used as a gating period, during which a single rising edge on input 2 will cause a logic 1 output-any other number, indicating non-identical frequencies causes a logic 0 output. ICla converts input 1 to a narrow pulse which initializes IC2 which....
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On the initial part of the positive half cycle, the voltage is changing rapidly from zero causing a large current to flow into capacitor C2. The current through C2 flows through R4, D3, and D4 into the gate of the TRIAC Q2 causing it to turn on very close to....
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Transistors Ql and Q2 make up the flip-flop while Q3 drives a reed relay. When power is first applied to the circuit, Ql and Q3 are conducting and Q2 is cut off. Momentarily closing SI causes the flip-flop to switch states—Ql cuts off and Q2 conducts. When....
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A high impedance input is provided by Ql, a general purpose field effect transistor..
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The battery powered light turns on easily, stays on for just a few seconds, and then turns off again. The circuit is triggered when you place a finger across the gap between two strips of metal, about l/16th inch apart. Enough current will flow through your....
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This circuit uses a 555 timer in the bistable mode. Touching T2 causes the output to go high; D2 conducts and D1 extinguishes. Touching T1 causes the output to go low; D1 conducts and D2 is cut off. The output from pin 3 can also be used to operate other....
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This circuit is actuated by an increase in capacitance between a sensing electrode and the ground side of the line. The sensitivity can be adjusted to switch when a human body is within inches of the insulated plate used as the sensing electrode. Thus,....
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The proximity sensor works on the principle of transmitting a beam of modulated infra-red light from the emitter diode LED2, and receiving reflections from objects passing in front of the beam with a photodiode detector Dl..