Top Circuits Page 5
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This wideband RF isolation amplifier has a frequency response of 0.5 to 400 MHz ± 0.5 dB. This two stage amplifier can be used in applications requiring high reverse isolation, such as receiver intermediate-frequency (IF) strips and frequency distribution....
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This 100 watt linear amplifier may be constructed using two MRF309 transistors in push-pull, requiring only 16 watts drive from 420 to 450 MHz..
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A unique push-pull parallel circuit. It uses four MRF150 RF power FETs paralleled at relatively high power levels. Supply voltages of 40 to 50 Vdc can be used, depending on linearity requirements..
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The circuit will find excellent usage in high frequency line driving systems that require wide-power bandwidths at high output current levels. (IC=HA2530) The bandwidth of the circuit is limited only by the single pole response of the feedback....
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The amplifier provides 10 dB of gain from 10-600 MHz and has a 1-to-l match at 50 ohms. The BFR91 has a 1 dB noise figures at 500 MHz, The circuit requires 13 Vdc at about 13 mA. Keep the leads on the 150 pF emitter bypass capacitor as short as possible. The....
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The amplifier operates across the 2 -30 MHz band with relatively flat gaio response and reaches gain saturation at approximately 210 W of output power. Both input and output transformers are 4:1 turns ratio (16:1 impedance ratio) to achieve low input....
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This amplifier utilizes a 2N6367 and a pair of 2N6368 transistors. The 2N6367 transistor is employed as a driver and is specified for up to 9 W (PEP) output. In the amplifier design the driver must supply on 5 W (PEP) at 30 MHz with a resulting !MD....
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The only adjustments that require close attention are input, output, and neutralization. The 150-pF capacitor in the input line compensates for impedance mismatch. You tune for maximum signal transfer from exiter to final with an in-line meter or external....
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The circuit has a frequency response ranging from 100Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Q1 is configured in the common-source self-biased mode. Optional resistor R1 allows you to set the input impedance to any desired value;....
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This wideband amplifier uses only five components. External signals enter pin 3 of IC1 via ac coupling capacitor Cl. Following amplification, the boosted signals from IC1 pin 1 are coupled to the output by capacitor C2. Capacitor C3 decouples the de....
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The amplifier"s input stage is a dual-gate GaAs FET, which provides low input capacitance and high transconductance. The dual-gate structure accepts the signal on input 1. Input 2 controls the gain of the amplifier. The amplifier has a third input for use....
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The design incorporates 30-0, 1/4;.. microstrip lines on the input and output. C3, C4, C7, and C8, along with Ll, form a pi network that matches the low-input impedance of the device to 50 0. C5, C6, C9, ClO, and 30-0 transmission line L2 form an output pi....
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This circuit design is a class A amplifier employing both ac and de feedback. Bias is stabilized at 15 mA of the collector current using de feedback from the collector. The ac feedback, from collector to base, and in each of the partially bypassed emitter....
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This amplifier provides 140-W PEP nominal output power when supplied with input levels as low as 3 W. Both input and output transformers have a 4:1 turn ratio and a 16:1 impedance ratio to achieve low input VSWR ..
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This circuit functions as a wideband adjustable AGC amplifier. With an effective bandwidth of approximately 10 MHz, it is capable of handling rf input signal frequencies from 3.2 to 10 MHz at levels ranging from 40 mV up to 3 V pk-pk. AGC action is....
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This circuit utilizes the MRF123 TMOS power FET. The MRF134 is a very high gain FET that is potentially unstable at both VHF and UHF frequencies. Note that a 68-0 input loading resistor has been utilized to enhance stability. ..
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This 60-W. 28-V broadband amplifier covers the 225-400 MHz military communications band. The amplifier may be used singly as a 60-W output stage in a 225-400 MHz transmitter. or by using two of these amplifiers combined with quadrature couplers, a 100-W....
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The circuit protects a solid-state relay from overloads. The circuit limits current, automatically disconnects the load after ..
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The frequency range of this amplifier is 1.8 to 54 MHz. The amount of RF drive required for full output is about 30 W...
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100 W output at 50 MHz is available from this circuit. Ul and Q2 form a T-R relay driver, switching the amplifie..
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This amplifier is useful for applications where a 10- to 15-W peak-envelope-power (PEP) signal is needed i..
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This circuit offers 10- to 15-dB gain from 400 to 850 MHz and is therefore eminently suitable for situations where th..
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Using an NEC70083, this 1296-MHz amplifier delivers about 17-dB gain and around 1- to 1.5-dB noise. It is constructed..
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The use of a loop antenna of large size (12 18") provides a large signal pickup at AM broadcast frequencies. It has..
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This HF SW receiver preamplifier is comprised of a broadband toroidal transformer (LI-a and Ll-b), a complex LC network (comprised of a 1600- kHz, high-pass filter and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon....
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The circuit has a frequency response that ranges from 100 Hz to 3 MHz; the gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor R1 allows you to set the input impedance to any desired value.....
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The SD1143 transistor provides a gain of about 14 dB in this circuit. It uses the fact that a 175-MHz device has a much higher gain when used at lower frequencies. The amplifier was originally designed to be used with a transverter. ..
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Except for the coupling and decoupling capacitors, IC1 is a complete wideband amplifier that has a fixed gain of 20 dB to 450 MHz. No external compensation is required. since the NE5205 functions as a gain block, two or more cart be easily cascaded to....
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This linear amplifier delivers 10-W PEP output; with 1.25-W drive on 10 m. Tl, T2, and T3 are 10 turns of bifilar windings on an FT-50-43 toroidal core. The transformers are broadband. Filters for other bands, if desired, are shown. Note: use #26 wire for....
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The low-cost Mini-Circuits MAR-X series of chips offer the RF builder a real advantage, with their inherent 50- input and output impedances (needed for RF systems). An MAR-1-based receiver/scanner preamplifier is shown. Ci and C2 are chip capacitors. Use....
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The circuit, shown will produce up to 5-W RF output in the 40-m (7 MHz) amateur band. The coils shown are wound on toroidal cores (Armdon Associates Inc.). The part numbers are given in the schematic...
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Motorola MWA 110, 120, or 130 are wideband amplifier ICs. This wideband preamp circuit can be used in many applications. Keep the leads short when constructing the circuitry. PC board layout (shading represents copper) and parts layout. X is the feedthrough....
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Before power is applied, the input and output are at ground potential and capacitor C is discharged. On power-on, the output goes high (Vdd) and C charges through R until V is reached; the output then goes low (Vss). C is now discharged through R until Vn is....
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This dual astable multivibrator provides versatility not available with single timer circuits. The duty cycle can be adjusted from 5% to 95%. The two outputs provide two phase clock signals often required in digital systems..
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The 4047 is configured as a free-running, astable- multivibrator (oscillator) circuit. That configuration, offers three different outputs. The output pulses at the Q and Q output (pins 10 and 11, respectively) are the same as in the previous two....
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Uses CA3130 BiMOS op amp that operates at a frequency of 1 kHz. With rail-to-rail output swing, frequency is independent of supply voltage, device, and temperature. ..
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This astable will trigger itself and run free as a multivibrator. The external capacitor charges through RA and RB and discharges through R8 only. Thus, the duty cycle is set by the ratio of these two resistors, and the capacitor charges and discharges....
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The power bandwidth of the HA-5147 extends the circuit"s frequency range to approximately 500 kHz. R, can be made adjustable to vary the frequency ifdesired. Any timing errors because of Vas or hu., have been minimized by the precision characteristics....
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Three factors contribute to the output symmetry. The capacitor charges and discharges through the same external resistor. An internal resistive divider sets accurate switching thresholds within the chip, the bipolar types use dividers, as well. Most....
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The circuit shows a simple yes/no gas detector. Three 1.5-V D cells are used as a power supply, with SI acting as an on/off switch. The heater is energized directly from the battery, while the electrodes are in series with a 10 k resistor. The voltage across....
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Sensing circuit detects either steady or fluctuating air flows. The heart of the circuit is a Radio Shack piezo buzzer (P/N 273-060) and an LM324 quad op amp. (Red wire from the piezo element connects to capacitor CI, and the black wire to ground) When a....
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This circuit can detect smoke and a number of gases (CO, CO2, methane, coal gas and others) with a 10 ppm sensitivity. It uses a heated surface semiconductor sensor. Detection occurs when the gas concentration increase causes a decrease of the sensor element....
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Battery-operated, ionization chamber smoke detector includes a circuit to generate a unique alarm when the battery reaches the end of its useful life. The circuit uses the MCMOS MC14572 for two alarm oscillators (smoke and low battery)..
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The LED predriver output pulses an external transistor which in turn, switches on the infrared light emitting diode at a very low duty cycle. The desired IR LED pulse period is determined by the value of the external timing resistor. The Smoke Sensitivity is....
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ICl, an Intersil ICL 7106, contains an aid converter, a 3,1/2-digit LCD driver, a clock, a voltage reference, seven segment decoders, and display drivers. A similar part, the ICL7107, can be used to drive seven segment LEDs. The probe body is a five-inch....
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Use CA3164A BiMOS detector/alarm system. For operation as smoke detector with electromechanical hom (Fig. 40-la), the output of driver at terminal 8 is used. Large npn transistor Q3,-with an active pull-up and transistor Q2 provide over 300 mA of drive....
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Transformer T1 supplies power to the heater of the sensor. Since the sensor is fairly sensitive to heater voltage, diodes Da, D4, and D5 regulate the heater voltage. Tl, together with D1 and CZ, forms a de power supply, whose current is regulated by Q1 and....
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The sensor is based on the selective absorption of hydrocarbons by an n-type metal-oxide surface. The heater in the device serves to burn off the hydrocarbons once smoke or gas is no longer present in the immediate area; hence, the device is reuseable.....
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This circuit can be used to measure exhaust gas temperature in a furnace. The 10-bit LTC1091A gives 0.5°C resolution over a ooc to 500°C range. The LTC1050 amplifies and filters the thermocouple signal, the LT1025A provides cold junction compensation and....
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This smoke detector uses a MEM 817 p-channel enhancement mode MOSFET as its buffer amplifier. Operation of the sensor is based on a decrease in the current when smoke enters the chamber, thereby causing a negative voltage excursion at the gate of the....
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In the presence of smoke or gas, the ac output voltage increases and becomes rectified, filtered and zener-diode coupled (D2 for thresholding) to sensitivity control R3. Under no gas condition, the output equals approximately 0 V (high). When gas is....
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This circuit comes from U.S. Patent 3, 778,800, granted to BRK Electronics in Aurora, IL. The circuit provides a smoke detector with an alarm for both smoke and low batteries. The R6/R7 voltage divider monitors the battery and will turn Q2 and Ql off when....
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When power is applied to the circuit, the heater coil in the sensor is energized by the 5-V output of IC5, a 7805 voltage regulator. Breathing into the sensor with alcohol on your breath will lower the sensor"s resistance; consequently, the input voltage....
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When a current of air hits tbe piezo element, a small signal is generated and is fed through Cl and Rl to inverting input pin 2 of one section of the LM324. That causes output pin 1 to increase. Resistor R3 is used to adjust the sensitivity of the....
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Using the thermistor-bridge circuit, you can detect system-cooling air losses caused by filter or inlet ..
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A piezoelectric detector (BZ1) is used in this circuit to detect a change in air pressure. BZ1 produces a volt..
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A bar-graph LED driver is used to drive 10 LEDs to give a relative indication of moisture. The moisture probes are connec..
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A gas sensor (TGS823 from Allegro Electronics, Cornwall Bridge, CT 06754) conducts in the presence of explosive gases. U5 is a voltage-to- frequency converter that produces a frequency proportional to the sensor conductance. The output frequency ranges from....
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THE GAS SENSOR is mainly composed of tin dioxide on a ceramic base; the resistance of the sensor varies depending on the concentration of reducing gases in the air. The circuit shown is useful for the detection of dangerous levels of combustible fumes or....
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The moisture detector uses two transistors and a piezoelectric transducer to sound an alarm tone when water is present. Transistor Ql forms a crystal-controlled oscillator, using a portion of piezoelectric transducer XDCwhich contains two piezoelectric....
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The circuit is basically a NE555 monostable, the only major difference being its method of triggering. The trigger input is biased to a high value by the 22 ohm resistor. When the contact plates are touched, the skin resistance of the operator will lower....
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A 3-x -3-inch piece of circuit board, or similar size metal object which functions as the pick-up sensor, is connected to the gate of Ql. A 100-MD resistor, R2, isolates Ql"s gate from Rl, allowing the input iropedance to remain very high. If a 100MO....
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The SillOO series circuit input is connected to a capacitive field sensor-possibly a piece of doublesided circuit board. Any induced voltage change on the plate is fed to the input of the peak detector section of the op-amp circuit. The Schmitt trigger....
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The 4047 is configured as a monostable multivibrator circuit or one shot that is set up to trigger on a negative-transition of the signal applied to its pin 6 input. The multivibrator"s on time is determined by the values of R1 and Cl. Although R1 is....
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LED1 and LED2 indicators turn on and remain on, each time the circuit is triggered. During the timing cycle, U1 "s Q output at pin 10 becomes positive when the Q output at pin 11 becomes negative. ..
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Only one LED can be on when the circuit is at rest. Which LED is illuminated is determined by the touch pick-up that last had human contact. Pickup terminal A controls the on condition of LEDl, and terminal B controls the on condition of LED2. ..
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This circuit requires the bridging of two circuits to activate the electronic switch. That circuit does not require a 60-Hz field to operate and can be battery or ac powered. The two-pickup terminals can be made from most any clean metal; they should be....
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The monostable period is set for about 1 second, as is the usual case. The induced line hum comes through C2, providing a continuous string of trigger pulses. The output becomes low for about 10 ms per second as the monostable times out and then....
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This touch-actuated switch stays on as long as you keep your finger on the touch plate. Rl sets the input impedance to a high 22 MO. Ql picks up stray signals coupled through your body to the touch plate and amplifies them to tum on Q2, which turns on lamp....
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By vocalizing the numbers and symbols of its~eypad, the phone provides an audible confirmation that is useful to the blind. The serial-interface, 2 K-byte x 8-bit ROM (!C4) stores programmed sequences of instructions that are executed by the....
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What makes this control unique is its momentum feature, which adds a degree of realism. The circuit will opera..
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This highly sensitive movement detector is designed from bipolar transistors and draws a curren..
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A high-frequency audio signal (15 to 25 kHz) generated by Ul is fed to buffer Ql and SPKR1. A portion is f..
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Ql is used as an oscillator around 300 kHz. R9 is set so that the oscillator just begins to run. An object ne..
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Right- and left-channel signals pass through 1 C4-a and -b buffer amps into active crossover IG5; low frequencies are sent to the IC6-c mixer, and middle and high frequencies are sent to the analog delay lines of 1C1 and 1C2. That output passes through....
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Using an ISD1016 audio record/playback chip (Information Storage Devices, Inc.), this circuit records and plays back messages on command. Although intended for use with transmitters, it can be used as an electronic notepad, etc. ..
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Using digital techniques, this circuit accomplishes the frequency-inversion algorithm via digitization of the audio, inversion of the sign of every alternate sample, and D/A conversion of the resultant data. The result is an inverted frequency spectrum...
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Integrated circuit gates ICl-a and TCl-b form a monostable, whose time constant is determined by C2 and R3. When the transmitter is dekeyed (and then almost immediately rekeyed) point TX+ goes low and takes pin 1 low for a short time. This triggers the....
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When the touch-on contacts are bridged, pin 6 of Ul-b goes low, which forces its output (the set output) at pin 4 to go high. That high divides along two paths; in one path, the output is applied to pin 2 of Ul-a, which causes its output at pin 3 to go low.....
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This device allows you to control remotely any (with suitable add-on expansion boards, up to eight) device, such as lights, water heaters (boiler), air-condition, plant watering, alarms, etc via a relay. By using it you can for example water the garden at....
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This document is an introduction to the Wideband Fuel Mixture Display (FMD). We modified the original Silicon Chip Fuel Mixture Display (that used a narrowband sensor) for use as a display for the DIY-WB wideband oxygen sensor controller. After first....
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The single-chip, burglar -alarm circuit shown uses a dual 556 timer, draws 10 mA of standby current, and generates a pulsing alarm signal that conserves battery energy. Once activated, the alarm wilLremain on, independent of the subsequent state of any of....
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False alarms produced by semiconductor failure are impossible with this burglar-alarm circuit equipped with relays. What"s more, the circuit is virtually immune to false triggering. With a standby current of less than 0.1 mA, the circuit offers all the....
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The heart of the circuit is a 555 oscillator /timer, Ul, configured for monostable operation. The output of Ul at pin 3 is tied to the gate of SCRl. As long as Sl-S5, which are connected to the trigger input of Ul, are open, the circuit remains in the....
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The tracer, consisting of both a transmitter and receiver, is designed to follow a closed-loop wire or cable system. It follows an induced voltage path created by feeding a low-current, audio-frequency signal through the cable. When the pick-up coils....
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When SI (sensor) is closed, power is applied to U2, a dual timer. After a time determined by C2, CI is ene..
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This alarm circuit activates when SI through S5 are activated. This lights LED1 and activates Ql via IC1C and IC1D. RY..
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This circuit uses a 556 to first generate a low frequency square wave, that is modulated to produce two alternate tones of about 400 and 500 Hz. Circuit generates warble alarm of European emergency vehicles. ..
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In the circuit, U1 amplifies the audio picked up by the condenser microphone. Resistor Rl limits current, while R2 and R3 center the output of the amplifier to %B+ to allow a single-ended supply to be used. Diodes D1 and D2 rectify the output of Ul, and C3....
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The alarm uses a fixed-frequency piezoelectric buzzer in conjunction with the cadmium-sulfide (CDS) cell and the two-transistor circuit to provide a unique effect. Whenever light reaches the CDS photo-electric cell, the alarm is silent. But when no light....
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The burglar chaser makes a great accessory for any alarm system. It creates brilliant flashes of white light and a loud, irritating sound from a metal horn buzzer. Transformer T1 is connected to Ql, Rl, and R2 to form a blocking oscillator. This creates a....
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The baby-alert transmitter is built around an LM324 quad op amp (Ul), two LMC555CM CMOS oscillator/timers (U2 and U3), and a few support components. The transmitter sends a signal on receipt of a sound at MIC1...
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The baby-alert receiver is comprised of three transistors: Q2, which is configured as a high-gain linear amplifier; Q3, which serves as both an amplifier and detector; and Q4. which is essentially used as a switch; and a few additional components...
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This circuit is useful if you need a low-energy flashing alarm. The 200 to 400-dc supply should have enough internal resistance to charge the 0.5 capacitor between flashes, about 2 or 3 time constants, which means about 500 kQ to 1 for a 1-s rate. ..
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IC1 contains several oscillators and an amplifier. The low-frequency audio-signal oscillator is used to supply an input to the amplifier. That signal is the audio tone that is amplified, then supplied to the speaker by the amplifier. The high-frequency....
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This circuit uses inexpensive, common components to generate a precise dial tone for phone applications (see the figure). Ul (an Intel 82C54 timer-counter) generates 350 and 440Hz square waves that are filtered by Rl/Cl and R,JC2, and mixed together by....
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Field effect transistor, Ql, operates in the linear resistive region to provide automatic gain control. Because the attenuation of the RC network is one-third at the zero phase-shift oscillation frequency, the amplifier gain determined by resistor R2 and....
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Wien bridge sine-wave oscillator using two RCA CA3140 op amps cover» 30 Hz to 100 kHz with less than 0 percent total harmonic distortion. The 10k pot is adjusted for the best waveform..
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Circuit uses a simple RC network to produce an exceptionally shrill tone from a miniature speaker. With the parts values shown, the circuit oscillates at a frequency of 3 kHz and drives a miniature 2W speaker with ear-piercing volume. The output waveform is....
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Circuit oscillates because the transistor shifts the phase of the signal 180° from the base to the collector. Each of the RC networks in the circuit is designed to shift the phase 60° at the frequency of oscillation for a total of 180°..