Circuit Diagram

DUAL_VOLTAGE_RECTIFIER_CIRCUIT

Published:2009/6/26 4:27:00 Author:May

This stepped-up dual voltage supply provides ±15 to ±18V unregulated.   (View)

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VHF_PREAMPLIFIER

Published:2009/6/26 4:27:00 Author:May

This simple circuit gives 15 dB gain and can be mounted on 1 in 2PCB. Coil data is given for 85 to 95 MHz. For other frequencies modify coil as required.   (View)

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SHORTWAVE_FET_BOOSTER

Published:2009/6/26 4:26:00 Author:May

This two transistor preselector provides up to 40 dB gain from 3.5 to 30 MHz. Q1 (MOSFET) is sensitive to static charges and must be handled with care.   (View)

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SINGLE_TRANSISTOR_PHASE_SHIFTER

Published:2009/6/28 20:40:00 Author:Jessie

This circuit provides a simple means of obtaining phase shifts between zero and 170°.The transistor operates as a phase splitter, the output at point A being 180° out of phase with the input. Point B is in phase with the input phase. Adjusting R1 provides the sum of various proportions of these and hence a continuously variable phase shift is provided. The circuit operates well in the 600 Hz to 4 kHz range.   (View)

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SUBWOOFER_AMPLIFIER_POWER_SUPPLY

Published:2009/6/26 4:26:00 Author:May

Although intended to power a 100-W low-frequency amplifier, this power supply should handle many mono or stereo amplifiers in the medium power range that require ±30 to 35 V.   (View)

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lO_MHz_COAXIAL_LINE_DRIVER

Published:2009/6/26 4:22:00 Author:May

The circuit will find excellent usage in high frequency line driving systems that re-quire 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 components; namely f(-3 dB) = 1/2 πRfCf. As such, the response is flat with no peaking and yields minimum distortion.   (View)

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PHASE_SEQUENCE_INDICATOR

Published:2009/6/28 20:39:00 Author:Jessie

Simple, portable phase-sequence indicator determines the proper phase rotation in polyphase circuits. Major components are two neon lamps, two resistors, and a capacitor. In operation, the leg voltages are unbalanced, so that the lamp with the maximum voltage—or proper phase sequence—lights. Table shows typical component values for various circuit frequencies.   (View)

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ac_VOLTAGE_PROBE

Published:2009/6/26 5:32:00 Author:Jessie

This simple probe can save your life by waming you of live circuitry. It's ideal for times when more than one person is working on a device.   (View)

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SIMPLE_VOLTAGE_PROBE

Published:2009/6/26 5:31:00 Author:Jessie

This simple voltage probe can be helpful in checking and troubleshooting solid-state circuitry.   (View)

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TELECOM_CONVERTER_－48_V_TO_5_V＠1_A

Published:2009/6/26 5:29:00 Author:Jessie

The circuit supplies 1 A at +5 V from the -48-V supply commonly used in telephone equipment. The National Semiconductor LM2575 is a simple switching regulator.   (View)

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ADD_12_V_OUTPUT_TO_5_v_BUCK_REGULATOR

Published:2009/6/26 5:27:00 Author:Jessie

By adding a flyback winding to a buck-regulator switching converter (see the figure), which is essentially a 5-V supply with a 200-mA output capability, a 12-V output (VPP) can be produced. The flyback winding on the main inductor (forming transformer T1) enables an additional low-dropout linear regulator (IC2) to create the 12-V output voltage that's needed to program EEPROMs. The required input voltage is 8 to 16 V.   (View)

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24_V_TO_33_V_SWITCHING_REGULATOR

Published:2009/6/26 4:08:00 Author:May

The National Semiconductor LM2574 delivers 3.3 V out at O.SAfrom a 24-V source. The duty cycle is:VD ＝ diode drop(0.39)VIND ＝ inductor dc dropVSAT ＝ saturation voltage of LM2574(0.9 V typical)   (View)

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_5_V_SUPPLY

Published:2009/6/26 5:24:00 Author:Jessie

The power supply shown is designed to operate from a wall transformer. This circuit can be used in conjunction with a variable supply to test circuits in the lab, etc. T2 is a 12-V wall transformer.   (View)

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AUDIO_CONTINUITY_TESTER

Published:2009/6/26 4:05:00 Author:May

This low-current audio continuity tester indicates the unknown resistance value by the frequency of audio tone. A high tone indicates a low resistance, and a tone of a few pulses per second indicates a resistance as high as 30 megohms.   (View)

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5_V_UPS

Published:2009/6/26 5:22:00 Author:Jessie

A 9-V wall adapter supplies VIN. IC2 contains a low-battery detector circuit that senses VIN by means of R6 and R7. The detector output (pin 7) drives an inverter (Q1), which in tum drives the shut-down inputs IC of IC1 and SHDN of IC2. These inputs have opposite-polarity active levels. The common feedback resistors, R2 and R3 enable both regulators to sense the output voltage, VOUT. When IC2 shuts down, its output turns off. However, when IC1 shuts down, the whole chip assumes a low-power state and draws under 1 μA. L1, D2, C1, C2, R2, and R3 are part of the 250-mW switching regulator. Diodes D3 and D4 wire-OR the power connection to IC2, and C3 improves the linear regulator's load regulation.   (View)

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5_V_TO_33_V_SWITCHING_REGULATOR

Published:2009/6/26 4:05:00 Author:May

A National Semiconductor LM2574 is used to derive 3.3 V at 0.5 A from a 5-V logic bus. The duty cycle is: VD = diode drop (0.39) VIND = inductor dc drop VSAT = saturation voltage of LM2574 (0.9 V typical) This circuit should be useful to derive 3.3 V for logic devices from existing +5-V buses.   (View)

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INEXPENSIVE_ISOLATION_TRANSFORMERIMPROMPTU_SETUP

Published:2009/6/26 5:17:00 Author:Jessie

Using two 12-V filament or power transformers, an impromptu isolation transformer can be made for low-power(under 50 W) use in testing or servicing. SO1 is an ordinary, duplex ac receptable. Use heavy-wire connections between the 12-V windings because several amperes can flow.   (View)

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LOW_PARTS_COUNT_RATIOMETRIC_RESISTANCE_MEASUREMENT

Published:2009/6/26 4:04:00 Author:May

The unknown resistance is put in series with a known standard and a current passed through the pair. The voltage developed across the unknown is applied to the input and the voltage across the known resistor applied to the reference input. If the unknown equals the standard, the display will read 1000. The dis-played reading can be determined from the following expression:Runknown Displayed Reading= ___________ =×1000 RstandardThe display will overrange for Runknown, ≥2× Rstandard.   (View)

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ANTIQUE_RADIO_dc_FILAMENT_SUPPLY

Published:2009/6/26 5:11:00 Author:Jessie

This dc supply is great for operattng battery-powered anuque radios, because it is designed to prevent harming the tube filaments. The circuit is useful for powenng filaments of 00-A, 01-A, 112A，and 71A tubes, which requlre 5V at 250 mA.   (View)

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_15_V_SUPPLY_FOR_ZN416E_CIRCUITS

Published:2009/6/26 5:07:00 Author:Jessie

This regulator can be used with a +6-V source to supply ZN416E low-voltage TRF radio-receiver IC the necessary +1.5 V. R3 sets output voltage.   (View)

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