Precision Current Source

The 2N5457 and PN2222 bipolar serve as voltage isolation devices between the output and the current sensing resistor, R1. The LM101 provides a large amount of loop gain to assure that the circuit acts as a current source. For small values of current (<1 mA), the PN2222 and 10K resistor may be eliminated with the output appearing at the source of the 2N5457.Click para ampl...

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Precision Current Sink

The 2N5457 JFET and PN2222 bipolar have inherently high output impedance. Using R1 as a current sensing resistor to provide feedback to the LM101 op amp provides a large amount of loop gain for negative feedback to enhance the true current sink nature of this circuit. For small current values, the 10 K resistor and PN2222 may be eliminated if the source of the JFET is connected to R1.Click para ampl...

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Precision 1uA to 1mA Current Sources

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Current Source for Low Resistance Measurements

Useful for low-resistance measurements, this 1-A current source will produce 1 A in unknown resistance Rx. For best results, Rx should be less than 1 to 2 ohms, because only 3 V are available. U1 is a flyback converter to generate 9 V for U2.Click para ampl...

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Current Source

This precision current source has 10 uA to 10 mA ranges with output compliance of 30V to -5V. Output current is fully adjustable on each range with a calibrated, ten-turn potentiometer. Error light indicates saturation.Click para ampl...

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Introducción

El comportamiento de cualquier circuito eléctrico, del que se conozca su configuración, así como los elementos que lo integran y las condiciones iniciales de funcionamiento, puede determinarse mediante las dos leyes de Kirchhoff y las ecuaciones de tales elementos.Determinar el comportamiento de un circuito es hallar la expresión de la tensión y de la intensidad correspondiente a cada elemento, conocidas las fuentes de excitación, la carga o la tensión inicial de cada condensador y el flujo o la intensidad de corriente inicial de cada bobina. Para...

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Terminología de Redes

Rama: Es un elemento o grupo de elementos que presenta dos terminales. Algunas veces se denomina también lado. Únicamente consideraremos que una agrupación de elementos de dos terminales A y B forma una rama, cuando se conocen los parámetros y la relación que liga la tensión entre A y B con la intensidad que pasa a través de esos terminales. En particular, pueden considerarse constituyendo una rama aquellos elementos que son del mismo tipo, y pueden...

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Análisis de Redes Mediante Ecuaciones de Variables de Rama

El primer paso para el análisis de un circuito está en la determinación de todas las ecuaciones disponibles, de las cuales, posiblemente algunas sean combinaciones lineales del resto, por lo que el paso definitivo será encontrar cuales de entre todas son ecuaciones linealmente independientes.Número de Ecuaciones DisponiblesEstudiaremos este problema sobre el grafo de un circuito genérico. Admitiremos de momento, que tal circuito es pasivo, y que...

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Ramas con Fuentes. Ecuaciones de Definición

En todo circuito con elementos disipativos, es decir, con resistencias, la corriente se mantiene a expensas de fuentes que van proporcionando la energía que se disipa.Puede darse el caso, como hemos indicado antes, de corriente producida a costa de la energía almacenada inicialmente en algún elemento no disipativo del circuito, pero esta energía ha de estar necesariamente acotada, por lo que la corriente debida a esta causa se ha de extinguir pasado...

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Modificaciones de la Geometría de un Circuito

En ocasiones, debido en general a hipótesis simplificadoras, podrán aparecer en un circuito ramas activas en que se tiene un elemento en serie con un generador de intensidad ideal, o bien un generador de tensión ideal en paralelo con otro elemento. En ambos casos, ya vimos que, a efectos del resto de circuito, esos elementos pueden quitarse en el análisis, por lo que volveríamos a tener la Fig. 6. (Esto es válido siempre que el elemento no presente...

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Circuitos Duales

La Teoría de Circuitos tiene como fundamentales las Leyes de Kirchhoff:1ª Ley: La suma algebraica de las intensidades que circulan por todas las ramas que cortan un recinto cerrado es igual a cero: Σi = 0.2ª Ley: La suma algebraica de las tensiones de las ramas que forman un circuito cerrado es igual a cero: Σu = 0.Se observa la dualidad entre estas leyes básicas con las palabras tensiónintensidad y recinto cerrado-circuito cerrado que pueden considerarse...

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Low Frequency Prescaler

For multiplying frequencies in the 1-to 150-Hz range, this circuit uses a 4046B and a divide 100 prescaler. The VCO output is phaselocked to the low-frequency input. This simplifies use of a frequency counter to measure LF signal frequencies. By using a 4017B and a 1-kHz fIN, the circuit can be used as a 1-to 9-kHz frequency synthesizer or as a x10 frequency multiplier.Click para ampl...

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10Mhz Frequency Counter

The circuit consists of ICM7208 seven-decade counter U1, ICM7207 oscillator controller U2, and CA3130 BIFET op amp U3. IC U1 counts input signals, decodes them to 7-segment format, and outputs signals that are used to drive a 7-digit display. IC U2 provides the timing for U1, while U3 conditions the input to U1. The 5.24288-MHz crystal frequency is divided by U2 to produce a 1280-MHz multiplexing signal at pin 12 of U2. That signal is input to pin...

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1.2Ghz Frequency Counter

The output of the CA 3179 is fed through the D1/Q1 circuit. Those components serve to boost the 1-V output of the CA3179 to a standard TTL level. Then, depending on the position of range switch S2b, the signal is passed directly to the 7216, or through the divide-by-four circuit built from the two D flip-flops in IC3.The other half of the range switch S2a controls the voltage at pin 3 of the CA3179. When pin 3 is high, the signal applied to pin 9...

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Voltage to Pulse Duration Converter

Voltage levels can be converted to pulse durations by combining an op amp and a timer IC. Accuracies to better than 1% can be obtained with this circuit (a), and the output signals (b) still retain the original frequency, independent of the input voltage.Click para ampl...

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Voltage to Current Converter 2

The current out is Iout =Vin/R. For negative currents, a PNP can be used and, for better accuracy, a Darlington pair can be substituted for the transistor. With careful design, this circuit can be used to control currents of many amps. Unity gain compensation is necessary.Click para ampl...

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Voltage to Current Converter

This voltage to current converter uses three op amps to drive a pair of power transistors. The current output is calculated as: Iout = Vin / R6Output resistance is over 50 Mohms. Iout can range from 1 mA to the current ratings of T1 and T2.Click para ampl...

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VLF Converter

The VLF Converter can be used to pick up signals for the general coverage of shortwave receivers. A number of unusual signals can be heard on frequencies below 15 kHz. This converter will convert frequencies from 0 to 250 kHz to 3500 to 3750 kHz so that the LF- and VLF-band segments can be received on an amateur or shortwave receiver that covers 3500 to 400 kHz. Signals from a short whip antenna (8 to 10 feet) are coupled through low-pass filter...

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Temperature to Frequency Converter 2

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Temperature to Frequency Converter

In this circuit an LM34 or LM35 produces a frequency proportional to temperature. Reference current (138mA) is set via R3. The output can be used to drive a display, frequency counter, or other indicating device for temperature readout.Click para ampl...

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Sine Wave / Square Wave Converter

An op amp used as a comparator produces a 10-V p-p square-wave output with 100-mV input, to 15 kHz. Adjust R5 for symmetry of square wave at low input levels.Click para ampl...

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Shortwave Converter for AM Car Radios

Using a Signetics NE602, this converter tunes the 9.5- to 9.8 MHz range. An AM car radio is used as a tunable IF amplifier. Output is taken from J2, the auto antenna. The crystal (XTAL1) can be a frequency about 1 MHz below the desired tuning range; for 9.5 to 9.8 MHz, an 8.5- to 8.8-MHz crystal should be used.Click para ampl...

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Power Voltage to Current Converter

Low cost converter is capable of supplying constant ac currents up to 1 A over variable loads.Click para ampl...

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Positive to Negative Converter

The transformerless dc-dc converter derives a negative supply voltage from a positive. As a bonus, the circuit also generates a clock signal. The negative output voltage tracks the dc-input voltage linearity (a), but its magnitude is about 3 V lower. Application of a 500-W load, (b), causes 10% change from the no-load value.Click para ampl...

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Pin Photodiode to Frequency Converter

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Period to Voltage Converter

ICA, R1, R2, R3, and Q1 form a current source. The current that charges C1 is given by:I= VDN x R1 (R1+R2) x R3= 15 x 3 kW (3kW +12kW) x 470kW= 6.4mAThe input signal drives ICD. Because ICD's positive input (V+) is slightly offset to +0.1V, its steady state output will be around +13V. This voltage is send to ICC thorough D2, setting ICC's output to +13V. Therefore, point D is cut off by D1, and C1 is charged by the...

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One Chip Crystal Controlled Converter

This circuit can work over a wide range of frequencies. XTAL 1 is a fundamental-frequency crystal. T1 and C1 are tuned to the input frequency. An application of this circuit is a simple shortwave converter for AM radios, etc. A tunable oscillator can also be used, as shown.Click para ampl...

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Ohms to Volts Converter

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Low Noise 420Mhz ATV Receiver/Converter

L1, Q1, L2 and L3 compose an RF amplifier stage that feeds M1, a doubly balanced mixer. Q4 is a local oscillator stage in the 375-MHz range. Signals in the 420- to 450-MHz range from Q1 are mixed in M1 and fed through filter L6/L7/C17, where only the 60- to 70-MHz (CH3/CH4) signals pass. The IF signal is passed to Q3, and IF amplifier. The overall gain is 25 dB and the noise figure less then 2 dB.Click para ampl...

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Low Frequency Converter

Among the signals below 550kHz are maritime mobile, distress, radio beacons, aircraft weather, European Longwave-AM broadcast, and point-to-point communications. The low-frequency converter converts the 10 to 500kHz LW range to a 1010 to 1550 kHz MW range, by adding 1000kHz to all received signals.Radio calibration is unnecessary because signals are received at the AM-radio's dial setting, plus 1MHz; a 100-kHz signal is received at 1100kHz, a 335-kHz...

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Light Intensity to Frequency Converter

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DC/DC Converter Circuit With 3.3 and 5V Outputs

Input voltages can range from 8 V to 30 V. The load range on the 5V is 0.05A to 5A while the 3.3-V load range is 0.1A to 1A. The circuit is self-protected under no-load conditions. Over all load and line conditions, including cross regulation, the 3.3-V output varies from 3.25V to 3.27V. The 5-V output varies from 4.81V to 5.19V under the same conditions.In a typical application to 0.5A on the 3.3V and 0.25A on the 5V, efficiency is typically 76%....

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