Published:2009/7/21 2:19:00 Author:Jessie
This simple Hartley JFET oscillator has a built-in zener-diode regulator to condition the power-supply voltage down to 9.1 V. L1 depends on the desired frequency. Typical values are C1=5 to 50pF variable, C2=100 pF plus a 3-to 30-pF trimmer, and L1=14μH (for 3.5 MHz). L1 should be mechanically rigid, should have an air core (do not use ferrite cores because of drift effects), and should have Q ≥ 200 for best stability. The tap will be typically 10 to 25 percent of the total turns. (View)
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Published:2009/7/8 23:11:00 Author:May
This preamp uses two ATF 13135 stages for typically 17-dB gain and less than 2 dB NF. (View)
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Published:2009/7/21 2:28:00 Author:Jessie
If the LO signal of the NE602 is sent directly to the output pins, the device can be used as a low-cost, high-frequency oscillator. (View)
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Published:2009/7/8 23:10:00 Author:May
The tremolo effect is generated by a repeating volume change at a rate usually between 1 and 15 Hz. The timer produces a low frequency square wave that is smoothed by a simple rc integrator. This varying signal modulates the signal input from the instrument. Transistor T1 is used as a voltage controlled resistor. The output of the circuit is connected in parallel to the output of the instrument. Potentiometer P1 provides depth control by adjusting the amplitude of the modulating waveform applied to the instrument. The rate control frequency is set by potentiometer P2. (View)
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Published:2011/8/2 2:23:00 Author:Rebekka | Keyword: Three-phase motor, phase failure protection
The circuit is composed of general purpose integrated operational amplifiers. The circuit is shown as above. It can be used in a variety of three-phase motor phase protections. IC uses a typical general-purpose integrated operational amplifiers, such as 5G24, BG305, FC4, F006, XFC77 or other foreign products μA741 etc. The relay J can use DC l2V operating voltage, the DC resistance is 200Ω DC relay. (View)
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Published:2009/7/21 2:39:00 Author:Jessie
Latch circuit using an LM3909 chip. Circuitry inside dashed lines is the LM3909, The circuit switches to and holds its condition whenever the switch changes sides (courtesy National Semiconductor Corporation). (View)
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Published:2011/8/2 2:24:00 Author:Rebekka | Keyword: Line current restrictor
The figure shows the current of the line current restrictor limit circuit. Once the value of the current exceeds the limit value, the controller relay will cut off the power supply immediately. The current limit value is continuously adjustable from l00mA to 10A. The components of the circuit is shown as above. The whole circuit includs the line current sample and voltage comparator, RS flip-flop and control relay. It is composed of an operational amplifier MA741 and a four - two input NAND gate CD4011. (View)
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Published:2009/7/21 2:41:00 Author:Jessie
Discrete level-shifting circuit (courtesy Motorola Semiconductor Products Inc.). (View)
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Published:2009/7/21 2:43:00 Author:Jessie
Pulse position modulator using an ECG955M timer/oscillator chip. The timer is connected as an astable multivibrator. With a modulating signal applied to pin 5 the pulse positon will vary with the modulating signal (courtesy GTE Sylvania Incorporated). (View)
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Published:2009/7/21 2:47:00 Author:Jessie
Cosine function from the 4301 multifunction chip (courtesy Burr-Brown Research Corporation). (View)
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Published:2011/8/2 2:25:00 Author:Rebekka | Keyword: Uninterruptible power supply
Uninterrupted power supply circuit composed of MIC5158 is shown as above. The circuit uses MIC5158 to control the uninterrupted power supply which formed by the source electrode of two N-channel tubes. The source electrodes of the 2 N-channel tubes are connected. This can avoid the current from passing the internal diode of integrated voltage regulator. This kind of low dropout regulator can control the battery switch rapidly. The most critical function of the exchange network line monitor is to the output voltage is lower than the designed limiting voltage when the batterr works online. (View)
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Published:2011/8/3 10:18:00 Author:Robert | Keyword: Driving, Transformer, Primary, Scondary
The picture shows the IGBT switch tube's driving circuit transformer primary and secondary principle circuit. The R235-R238 are grid electrode series resistance. It is important for IGBT grid electrode driving by selecting adequate grid electrode series resistors.Its openning and closing are achieved by the grid electrode circuit's charging and discharging. The grid electrode resistor with low value would make the grid electrode capacitot's charging and discharging be fast. So it would reduce the switching time and switching power consumption. When it has short circuits or it is during the closing time of fly-wheel diode which has bridge connection to the crossing IGBT, the added du/dt on the IGBT and its collector polar's a grid electrode capacitor could cause the case that there is current through the grid electrode circuit. If this current is large enough, this would generate voltage between grid electrode resistors and make the IGBT be wrong connected. (View)
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Published:2009/7/21 2:48:00 Author:Jessie
The figure shows a prototype strip tine oscillator that is capable of providing an operating range of 3.5:1 before oscillation ceases Length A∶40 mm,width B∶2 mm,width C:1 mm To change the frequency range,alter the length A and the length of the output coupling wire Typical frequencies with C=0 pF are about 145 MHz;with 27 pF, about 80 MHz; with 56 pF, about 60 MHz;and with 150 pF, about 36 MHz (plate-ceramic capacitors). With 1/16-inch double-sided PC board, note that the bottom ground plane covers the whole of the board. The output is about 0 dBm. The U310 FET is pushed through from the bottom side of the PC board until it touches the ground plane and is soldered directly to the ground plane. (View)
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Published:2009/7/21 2:49:00 Author:Jessie
True PMS circuit using one AD531 multiplier/divider and two AD741 op amps. The AD531 is combined with a simple filter to obtain the true PMS value of an AC input signal. By scaling VOUT=10 volts DC for a ±10-volt DC input this circuit can give direct RMS readings for 100 hertz to 100 kilohertz sine waves from 0.2 volt to 7.0 volts peak (courtesy Analog Devices, Inc.). (View)
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Published:2009/7/8 23:09:00 Author:May
This fteld-strength meter is useful for antenna testing. It covers 6 to 60 MHz and uses a rugged 0-to-1 mA meter. A 9-V battery supplies power. The unit can be mounted in a small plastic or metal case. (View)
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Published:2009/7/21 2:50:00 Author:Jessie
4-to-20 ma current transmitter (courtesy Analog Devices, Inc). (View)
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Published:2011/8/2 2:26:00 Author:Rebekka | Keyword: Negative pressure switch, Vacuum switch regulated power supply
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Published:2011/8/3 2:40:00 Author:Rebekka | Keyword: Automatic reset, Over-voltage protection
The circuit includes 3 circuit parts:power supply, trigger start and control. The power supply switch of the load R1 is controlled by bidirectional thyristor ZN6346. When the AC voltage is over high, the A point voltage of steady flow component 1N5314 will rise and the unidirectional thyristor will be conducted and the transistor will be closed. The main bidirectional thyristor will be closed at the same time, the load will be protected from damaging. (View)
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Published:2011/8/3 2:41:00 Author:Rebekka | Keyword: Storehouse temperature measurement alarm
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Published:2011/5/10 2:30:00 Author:Rebekka | Keyword: regulated power supply
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