Circuit Diagram

_5_V__36_V_FROM_4_AA_CELLS

Published:2009/6/25 2:28:00 Author:Jessie

With this unique logic-power-converter design (see the figure), a switchable 3.6 or 5 V at 200 mA can be attained by using four AA cells. The supply incorporates a MOSFET switch that can switch to a lithium backup battery, providing a 3.4-V output when the main battery is dead or removed. The supply consumes only 380 pA under no-load conditions. The circuit operates in a somewhat novel mode as a step-up/step-down converter. When the cells are fresh (from about 6 V to about 5.2 V), the LT1173's gain block drives the p-channel MOSFET, which turns the circuit into a linear voltage regulator. This might seem inefficient, but the batteries are quick to drop from 6 V to 5 V. With a 5-V input, the efficiency (for the 3.6-V output) is 3.6/5 or 72%, which is reasonable. As the battery-pack drops in voltage, efficiency increases, reaching greater than 90% with a 4.2-V input. At a point below a 4-V input, the circuit switches to step-up mode. This mode squeezes the bat-teries for all of their available energy. In this case, efficiency runs between 83% at approximately a 4-V input to 73% at a 2.5-V input. The supply can deliver 200 mA over its entire operational range. In its linear mode of operation, the supply has no current spikes that, because of the fairly high internal resistance of the alkaline cells, can reduce battery life. The topology delivers over 9.3 hours of 3.6-V 200-mA output power, compared to just 7 hours using the traditional flyback topology that is used in other designs.   (View)

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2LIGHT_METER

Published:2009/6/25 2:25:00 Author:May

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LIGHT_INTENSITY_TO_FREQUENCY_CONVERTER

Published:2009/6/25 2:28:00 Author:Jessie

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VOLTAGE_TO_CURRENT_CONVERTER

Published:2009/6/25 2:24:00 Author:May

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 cir-cuit can be used to control currents of many amps. Unity gain compensation is necessary.   (View)

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PRECISION_PHOTODIODE_COMPARATOR

Published:2009/6/25 2:28:00 Author:Jessie

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1LIGHT_METER

Published:2009/6/25 2:24:00 Author:May

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3LIGHT_METER

Published:2009/6/25 2:27:00 Author:Jessie

This light meter has an eight-decade range. Bias current compensation can give input current resolution of better than ±2 pA over 15 ℃ to 55℃.   (View)

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MILLER_OSCILLATOR_CRYSTAL_CONTROLLED

Published:2009/6/25 2:24:00 Author:May

Circuit Notes The drain of the JFET Miller oscillator is tuned to the resonant frequency of the crystal by an LO tank circuit.   (View)

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PRECISION_CLOCK_GENERATOR

Published:2009/6/25 2:23:00 Author:May

Circuit NotesThe CMOS IC directly drives 5 TTL loads from either of 2 buffered outputs. device operates to 10 MHz and is bipolar, MOS, and CMOS compatible.   (View)

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BUTLER_EMITTER_FOLLOWER_OSCILLATOR（20_MHz）

Published:2009/6/25 2:26:00 Author:Jessie

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WIDEBAND_HIGH_CREST_FACTOR_RMS_TO_DE_COMVERTER

Published:2009/6/25 2:26:00 Author:Jessie

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POLARITY_CONVERTER

Published:2009/6/25 2:22:00 Author:May

The capacitor-diode output circuit is used here as a polarity converter to generate a -5 volt supply from +15 volts. This circuit is use-ful for an output current of up to 20 mA with no additional boost transistors required. Since the output transistors are current limited, no addi-tional protection is necessary. Also, the lack of an inductor allows the circuit to be stabilized with only the output capacitor.   (View)

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LOGARITHMIC_LIGHT_METER_CIRCUIT

Published:2009/6/25 2:22:00 Author:May

The meter reading is directly proportional to the logarithm of the input light power. The logarithmic circuit behavior arises from the nonlineardiode pnjunction current/voltage relationship. The diode in the amplifier output prevents output voltage from becoming nega-tive (thereby pegging the meter), which may happen at low lightlevels due to amplifier bias currents. R1 adjusts the meter full-scale deflection, enabling the meter to be calibrated.   (View)

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2LIGHT_METER

Published:2009/6/25 2:25:00 Author:Jessie

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CURRENT_TO_VOLTAGE_CONVERTER_WITH_1_Accuracy

Published:2009/6/25 2:21:00 Author:May

A filter removes the dc component of the rectified ac, which is then scaled to RMS. The output is linear from 40 Hz to 10 kHz or higher.   (View)

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LINEAR_LIGHT_METER_CIRCUIT

Published:2009/6/25 2:21:00 Author:May

This circuit uses a low-input-bias op amp to give a steady dc indication of light level. To reduce circuit sensitivity to light, R1 can be reduced, but should not be less than 100 K. The capacitor values in the circuit are chosen to provide a time constant sufficient to filter high-frequency light variations that might arise, for example, from fluorescent lights.   (View)

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UNIVERSAL_LABORATORY_POWER_SUPPLY

Published:2009/6/25 2:21:00 Author:May

The value of the design lies in the use of IC1，an LM317HVK adjustable serles-pass voltage regulator，for broad-range performance remainder supplies voltage-setting and current limiting functions The input to IC1 comes from the output of BR1，which is filtered by C1 and C2 to about +60Vdc，and the input for current-sense comparator IC2 comes from BR2，which also acts as a negative bias supply for regulation down to ground. The output voltage is determined by∶( VOUT - 1.25 + 1.3 ) /( R15 + R16 ) ＝ 1.25 / R8.Thus，the maximum value from each variable supply board is∶VOUT = ( 1.25 / R8 ) × ( R15 + R16 ) = 50.18 Vdc   (View)

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TUBE_TYPE_CRYSTAL_OSCILLATOR

Published:2009/6/25 2:20:00 Author:May

Circuit Notes The pilot lamp limits current to prevent damage to the crystal.   (View)

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AC_TO_DC_CONVERTER

Published:2009/6/25 2:20:00 Author:May

This circuit includes a PMOS enhancement-mode FET input buffer amplifier, coupled to a classical absolute value circuit which essentially eliminates the effect of the forward voltage drop across diodes D1 and D2.   (View)

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PIERCE_HARMONIC_OSCILLATOR（BASIC_CIRCUIT）

Published:2009/6/25 2:20:00 Author:May

Circuit Notes This circuit operates 10-40 ppm above series resonance. It is a good circuit design with good to very good frequency stability.   (View)

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