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Index 176

HF_VFO_CIRCUIT

Published:2009-6-23 2:22:00 Author:Jessie

HF_VFO_CIRCUIT
This typical HF VFO circuit has several stability-enhancing features, including well-chosen capacitor types. The frequency of the VFO is approximately 2π (C1 + C2 + C3) L1. L1 should be an aircore type coil, rigidly mounted, with high (>200 value) value of Q.   (View)

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CAPACITOR_HYSTERESIS_COMPENSATOR

Published:2009-6-23 2:22:00 Author:Jessie

CAPACITOR_HYSTERESIS_COMPENSATOR
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GROUNDED_BASE_TUNED_COLLECTOR_OSCILLATOR_FOR_AM_BROADCAST_BAND

Published:2009-6-23 2:20:00 Author:Jessie

GROUNDED_BASE_TUNED_COLLECTOR_OSCILLATOR_FOR_AM_BROADCAST_BAND
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REINARTZ_OSCILLATOR

Published:2009-6-23 2:09:00 Author:Jessie

REINARTZ_OSCILLATOR
This oscillator uses mauctivity coupled emitter and collector windings to its main tank circuit.Take care so that L1 and L2 are not coupled to each other, otherwise this circuit is susceptible to parasitic at other frequencies.Typically ,L1 has 5 to 10 times the number of turns that L2 has.L1,L2,L3 are woundon same coil form. This oscillator is more suited to lower frequencies,≤10 MHz.   (View)

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PSEUDO_RANDOM_BIT_SEQUENCE_GENERATOR

Published:2009-6-23 2:09:00 Author:Jessie

PSEUDO_RANDOM_BIT_SEQUENCE_GENERATOR
In this circuit, an additional exclusive-OR gate is connected after the modulo-2 feedback, with C1 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 power-up. A shift-register length n of 10 is shown with feedback at stages 3 and 10, providing true and inverted maximal length sequence outputs. This technique applies an input directly to the feedback loop. Therefore, it's considered more reliable than applying an RC configuratior) to the shift-register reset input to create a random turnon state.   (View)

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AM_OSCILLATOR_FOR_WIRELESS_MICROPHONES

Published:2009-6-23 2:05:00 Author:Jessie

AM_OSCILLATOR_FOR_WIRELESS_MICROPHONES
This circuit will generate an AM-modulated signal in the AM broadcast band that can be picked up on a receiver.About 2V of audio input will produce about 30% modulation of the oscillator signal.An old AM broadcast oscillator coil or other two-winding coil with about a 10:1 turn ratio and about 50 to 150 μH inductance can be used for T1.   (View)

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JFET_VARIABLE_FREQUENCY_OSCILLATOR

Published:2009-6-23 2:01:00 Author:Jessie

JFET_VARIABLE_FREQUENCY_OSCILLATOR
This simple JFET-based variable-frequency oscillator can be used in receiver and transmitter circuits.   (View)

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STABILIZED_WIEN_BRIDGE_OSCILLATOR

Published:2009-6-23 1:50:00 Author:Jessie

STABILIZED_WIEN_BRIDGE_OSCILLATOR
In this application, the AD534 is used as a vari-able-gain amplifier for the feedback signal from the output to the Y input, via the Wien bridge. The peak-rectifter and filter combination applies sufficient voltage to the X (denominator) input to maintain a stable oscillation-amplitude (with about 0.2% ripple). At startup, because X is small (divider mode), the gain is high, and the oscillation builds up rapidly. This is but one of several possible schemes, involving no extemal active elerrtents. Its forte is simplicity, rather than high performance; nevertheless, the amplitude is not greatly affected by supply and temperature variations, about 0.003 dB per volt, and 0.005 dB per degree.   (View)

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UJT_100_kHz_CALIBRATION_OSCILLATOR

Published:2009-6-23 1:49:00 Author:Jessie

UJT_100_kHz_CALIBRATION_OSCILLATOR
This unusual 100-kHz oscillator (whose fre-quency is determined by XTALl) can be used as a marker generator to calibrate the analog diai of a communication receiver, or its output can be fed to a divider courtter to produce a stable lower-fre-quency output for use as a clock-signal generator.   (View)

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FET_VXO_CIRCUIT

Published:2009-6-23 1:49:00 Author:Jessie

FET_VXO_CIRCUIT
An MPF 102 is used in a Colpitts-type oscilla-tor in order to pull the crystal frequency slightly.   (View)

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dc_OUTPUT_CHOPPER

Published:2009-6-23 1:49:00 Author:Jessie

dc_OUTPUT_CHOPPER
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). Depending on the actual voltage of the supply, the programmable-unij unction-transist or (PUT) relaxation oscillator produces 2000-Hz trigger pulses. These pulses operate the cascaded 74C107 flip-flop, producing a square wave.   (View)

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CRYSTAL_OSCILLATOR_I

Published:2009-6-23 1:49:00 Author:Jessie

CRYSTAL_OSCILLATOR_I
In this circuit, series-resonant crystal XTAL1 is used as a frequency-determining element.XTAL1 is between 0.1 to 10 MHz.   (View)

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QUADRATURE_WAVE_OSCILLATOR

Published:2009-6-23 1:49:00 Author:Jessie

QUADRATURE_WAVE_OSCILLATOR
QUADRATURE_WAVE_OSCILLATOR
QUADRATURE_WAVE_OSCILLATOR

By using a high-frequency quad current-feedback amplifier (the HA5025) as an RC oscillator, four quadrature sine waves can be generated. The HA5025's four separate amplifiers generate the sine waves, and the quad NAND gate, U2, is biased at its threshold, so it acts as a sine-wave to square-wave converter when the she waves are ac coupled into its input.   (View)

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FET_QUARTZ_CRYSTAL_OSCILLATOR

Published:2009-6-23 1:48:00 Author:Jessie

FET_QUARTZ_CRYSTAL_OSCILLATOR
This oscillator uses an MPF102 JFET as an active element.   (View)

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VARIABLE_FREQUENCY_ASTABLE_II

Published:2009-6-23 1:43:00 Author:Jessie

VARIABLE_FREQUENCY_ASTABLE_II
This circuit uses a single potentiometer and switched capacitors to cover 2 Hz to 30 kHz。   (View)

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ASTABLE_OSCILLATOR_II

Published:2009-6-23 1:43:00 Author:Jessie

ASTABLE_OSCILLATOR_II
By using transistor switch Q1/R2/R3, the frequency of an astable oscillator can be changed with a dc voltage or logic level.   (View)

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ASTABLE_OSCILLATORI

Published:2009-6-23 1:41:00 Author:Jessie

ASTABLE_OSCILLATORI
ASTABLE_OSCILLATORI
ASTABLE_OSCILLATORI
ASTABLE_OSCILLATORI
ASTABLE_OSCILLATORI

In this circuit,two gates from the quad 4093 package are used to form a simple astable squarewave oscillator.The values for RX and CX are approximately as follows∶These values can be scaled for other frequencies.   (View)

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Simple Series Adjustable Regulator Circuit

Published:2011-7-18 5:26:00 Author:Felicity | Keyword: Simple Series Adjustable, Regulator Circuit

Simple Series Adjustable Regulator Circuit
Simple Series Adjustable Regulator Circuit
Simple Series Adjustable Regulator Circuit

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The low-noise and high-efficiency PWM step-down converting power supply circuit

Published:2011-7-24 3:29:00 Author:Seven | Keyword: low-noise, high-efficiency, power supply

The low-noise and high-efficiency PWM step-down converting power supply circuit
In the figure is the adjustable step-down power supply which is based on the low-noise and high-efficiency PWM converter MAX887(8-SO package), and the external elements are few. The characters of it are: (1) the input voltage is from 3.5V to 11.5V, the output voltage is 1.25V to 10.25V; (2) the output current is 600mA, and the static current is 200μA, the standby mode is only 2.5μA; (3) the converting efficiency is 95%; (4) the fixed working frequency of MAX887 is 300KHZ, which effectively reduces the size and cost of the external element.   (View)

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The +5V solid output step-down convert power supply circuit composed of MAX639

Published:2011-7-24 2:13:00 Author:Seven | Keyword: step-down, power supply

The +5V solid output step-down convert power supply circuit composed of MAX639
In the figure is the +5V solid output step-down convert power supply circuit composed of MAX639. MAX639 is a high-power step-down DC/AC converter. The input voltage ranges from 5.5V to 11.5V, the output is the +5V solid voltage or the adjustable voltage, the output current is 100mA, the converting efficiency is higher than 90%. The circuit has the function of low battery voltage detection and working/disable mode control.   (View)

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