Circuit Diagram

LCD_AUXILIARY_BIAS_CIRCUIT

Published:2009/7/16 23:11:00 Author:Jessie

This single-cell boost converter can generate the low supply voltages commonly needed in pagers and other portable instruments with small, graphic LCDs. The first is a regulated 3.3 V at 100 mA, and the other is a regulated negative output, suitable for use as an LCD bias voltage. The overall efficiency is about 80 percent. The main 3.3-V supply is provided by a boost converter (IC1). The auxiliary bias voltage is provided by an extra flyback winding (the T1 secondary), and is regulated via Q1 and the low-battery detector internal to IC1. As the battery discharges, its declining terminal voltage causes a decline in the voltage in the flyback winding. At minimum battery voltage (0.8 V), the T1 primary sees 3.3 V-0.8 V2.5 V, so the 6:1 turns ratio produces 6(2.5)=15 V in the secondary. At maximum battery voltage (1.65 V), the primary sees only 1.5 V, producing 9.9 V in the secondary. MOSFET Q1 stabilizes this output by interrupting the secondary current, introducing the regulation necessary to generate a constant negative output. The regulator uses IC1's low-battery detector (a comparator/reference combination) as an on/off controller for Q1. In this circuit, the R1/R2 divider holds LB1 between Vctrl (normally 3.3 V) and the LCD bias output (normally -8 V). R1 and R2 are chosen so that LBO turns off when the LCD bias becomes too negative (and pulls the LB1 voltage below 1.25 V). Load current then causes the LCD bias to drift upward (toward 0 V) until LB1 exceeds 1.25 V, which causes Q1 to turn on again. A logic signal at the LCD ON terminal provides a means to enable and disable the negative output.   (View)

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The biphasic pulse generator circuit composed of CD4013

Published:2011/8/4 8:20:00 Author:nelly | Keyword: biphasic pulse, generator

Inthedesignofthedigitalcircuit,wemayneedapairofbiphasicpulsegenerators.ThebiphasicpulsegeneratorcomposedofCD4013isasshown.(a)isschematic,and(b)isthewaveform.   (View)

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_20_V_FOR_VARACTORS

Published:2009/7/16 23:11:00 Author:Jessie

Precision low-ripple bias supply for varactor tuning applications can provide up to 20-mA output current.-M. A. Chapman, Multiple Band Master Frequency Oscillator, Ham Radio, Nov. 1975, p50-55.   (View)

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delay relay circuit composed by LM122

Published:2011/7/26 9:18:00 Author:Nancy | Keyword: delay relay

Figure 1 is the delay relay circuit composed by LM122. The LM122 is a timer integrated circuit from microsecond to hour level with a constant voltage circuit inside, so the timing is not effected by the change of the supply voltage, the output current is 50 mA and the working voltage is from 4.5 to 40 V. The Figure 1 (a) is a relay K energization circuit after the RtCt timing. When the relay loses electric, the external voltage +Ucc is off. The Figure 1 (b) shows that the relay K conducts and works with external voltage +Ucc and disconnects after the RtCt timing. The relay is off when you cut off the power again until the next operation.   (View)

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2_TO_6_V_CCFL_POWER_SUPPLY

Published:2009/7/16 23:04:00 Author:Jessie

The power supply shown operates from 2 to 6 V. It can drive a small (75-mm) CCFL over a 100-μA to 2-mA range. An LT1301 micropower dc-to-dc converter is used in conjunction with a current-driven Royer-class converter, consisting of T1, Q1, and Q2. When power is applied along with intensity-adjust voltage Va, the LT1301's Ilim pin is driven slightly positive, causing maximum switching current through the IC's internal switch pin (SW). L1 conducts current that flows from transformer T1's center tap, through the transistors, into L1. L1's current is taken in switched fashion to ground by the regulator's action. The Royer converter oscillates at a frequency primarily set by T1's characteristics (including its load) and the 0.068-μF capacitor. LT1301 drives L1, which sets the magnitude of the Q1-Q2 tail current, and thus creates T1's drive level. The 1N5817 diode maintains L1's current flow when the LT1301's switch is off. The 0.068-μF capacitor combines with L1's characteristics to produce sine-wave voltage drive at the Q1 and Q2 collectors. T1 provides voltage step-up and about 1400 V p-p appears at the transformer's secondary.   (View)

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VOLTAGE_CONTROLLED_AMPLITUDE_LIMITER

Published:2009/7/16 23:02:00 Author:Jessie

Amplitude-limiting circuits are useful when a signal should not exceed a predetermined maxi-mum amplitude, such as when feeding an A/D or a modulator. A clipper, which completely removes the signal above a certain level, is useful for many applications, but there are times when it is not desirable to lose information. The circuit in this figure is a voltage-controlled breakpoint amplifier. When the input signal reaches a predetermined level (the breakpoint), the amplifier gain is reduced. As both the breakpoint and the gain for signals greater than the breakpoint are voltage programmable, this circuit is useful for systems that adapt to changing signal levels. Adaptive highlight compression finds uses in CCD video cameras, which have a very large dynamic range. Although this circuit was developed for video signals, it can be used to adaptively compress any signal within the 40-MHz bandwidth of the LT1256. The LT1256 video fader is connected to mix proportional amounts of input signal and clipped signal to provide a voltage-controlled variable gain. The clipped signal is provided by a discrete circuit consisting of three transistors. Q1 acts as an emitter follower until the input voltage exceeds the voltage on the base of Q2 (the breakpoint voltage, VBP). When the input voltage is greater than VBP Q1 is off and Q2 clamps the emitters of the two transistors to VBP plus a VBE. Q3, an NPN emitter follower, buffers the output and drops the voltage (VBE); thus, the dc level of the input signal is preserved. The breakpoint voltage at the base of Q2 must remain constant when this transistor is turning on or the signal will be distorted. The LT1363 maintains a low output impedance well beyond video frequencies and makes an excellent buffer.   (View)

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STEP_UP_STEP_DOWN_REGULATOR

Published:2009/7/16 23:00:00 Author:Jessie

Adding a transformer to a step-up dc-to-dc regulator allows inputs of 20 V and higher to be accepted while operating in a step-down mode. The circuit handles inputs to 30 V, but is easily modifiable for high specific voltages. The transformer's 1:1 turns ratio simplifiers procurement by allowing the use of a standard, product (here, the Coiltronics CTX100-4P). Its 1:1 ratio also enhances stability by producing a duty cycle well below 50 percent. An ideal 1 : 1 transformer would generate Vin + Vout at the bottom of the primary, but real transformers produce somewhat higher voltages. That voltage appears across Q1, so Q1's minimum breakdown voltage should be approximately 2Vin +Vout. R2 limits the peak current (through Q1 and L1) to 0.33 A. The internal shunt regulator is a zener diode that is biased by R1 at approximately 2 mA. To cope with a wide range of input voltages, R1 can be replaced with a constant-current source.   (View)

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Quantitative Pulse Output Circuit With CD4046

Published:2011/8/4 8:25:00 Author:nelly | Keyword: Quantitative Pulse, Output

Quantitative Pulse Output Circuit With CD4046 is as shown   (View)

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PHOTOVOLTAIC_ISOLATOR_CIRCUIT

Published:2009/7/16 22:59:00 Author:Jessie

The advantage of the programmable junction transistor (PUT) over a P-MOSFET used as a gate pull-down is that the PUT will pull the gate well below the MOSFET threshold voltage much faster at lower cost. The PUT can discharge a gate capacitance of 5 nF at 12V in 100 ns.   (View)

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LOGIC_GATE_CURRENT_BOOSTER

Published:2009/7/16 22:58:00 Author:Jessie

By connecting all six gates of a 4049 hex inverting buffer in parallel, you can obtain a much higher output current than would otherwise be available.   (View)

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PULSE_AMPLITUDE_MEASUREMENT

Published:2009/7/16 22:57:00 Author:Jessie

Produces pulse whose width is linearly related to se looted portion of input signal. V42 is Schmitt trigger. V46 is flip-flop controlled by output from mognetron-beam switching tube (MBST) for selecting desired sample of signal. Output pulse width is sampled and measured by counter.-J. F. Lyons, Jr., Analyzing Multipath Delay in Communications Studies, Electronics, 32:36, p 52-55.   (View)

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0.1Hz～500kHz signal source circuit made by LM567

Published:2011/8/4 8:36:00 Author:nelly | Keyword: signal source

Manifold block LM567 is the high stability phase-locked loop circuit which has the phase-locked loop circuit. Using the internal “controllable current oscillator” of this manifold block can make a simple adjustable low-frequency signal source, so the maintenance will be very convenient. The circuit is as shown.   (View)

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PULSE_PHASE_SPLITTER

Published:2009/7/16 22:55:00 Author:Jessie

Provides bipolar pulses 180°out of phase, with perfect coincidence of positive-going leading edges, same reference level, and drive capability for saturated inverters.-G. Wolff, Simple Pulse Phase-Splitter, EEE, 14:2, p 70-72.   (View)

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BASIC_FULL_BRIDGE_CONVERTER_CIRCUIT

Published:2009/7/16 22:55:00 Author:Jessie

Today, most switching power supplies rated for more than 500 W are variations on the full-bridge converter topology shown. This design has four transistors; because diagonally opposite transistors are on at the same time, each transistor must have an isolated base drive. Full-bridge converters are usually manufactured as enclosed modules for such applications as powering mainframe computers and supercomputers.   (View)

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TRIGGER_GENERATOR

Published:2009/7/16 22:54:00 Author:Jessie

Differentiating circuit provides triggers for each input signal amplitude discontinuity, and resultant positive and negative triggers are converted to uniform negative polarity in paraphase amplifier V21A. Second channel, composed of overdriven amplifiers V25 and V26 and cathode follower V21B, provides output pulse whose width corresponds to that of overall input signal. lagging edge of pulse triggers one-shot V28 to generate delayed reset pulse for subsequent switching circuits.-J. F. Lyons, Jr., Analyzing Multipath Delay in Communications Studies, Electronics, 32:36, p 52-55.   (View)

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Multipurpose FM Signal Generator Circuit

Published:2011/8/4 8:54:00 Author:nelly | Keyword: Multipurpose, FM , Signal Generator

The figure is the multipurpose FM signal generator circuit. VTl and VT2 form the multivibrator. VT3 is the emitter-follower, which is used to modulate the signal source of VT4 oscillator. Then the signal will be emitted by Tx antenna.   (View)

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250_KC_MONO

Published:2009/7/16 22:53:00 Author:Jessie

When triggered by input pulse up to 5 V, switches to unstable state and remains for predetermined time before returning to original stable state. Used for standardizing random-width pulses and generating time-delayed pulses. Output pulse duration range is 2 microsec to 1 sec. Maximum input frequency is 250 kc.- Transistor Manual, Seventh Edition, General Electric Co., 1964, p 201.   (View)

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VSUBOUT_SUB__BOOSTER

Published:2009/7/16 22:53:00 Author:Jessie

Step-up dc-to-dc converters that operate from small input voltages often possess correspondingly low maximum breakdown voltages of 5 to 6 V. This limits the maximum output voltage available from such devices. However, by adding an autotransformer, the output voltage (Vout) can be doubled without exceeding the IC's breakdown voltage. A properly wound center-tapped inductor acts like a transformer with a 1 : 1 turns ratio. Combined with an IC that typically boosts single-cell inputs as high as 6 V, it produces a regulated 9-V output with no more than 4.5 V across the IC (Fig. 1). The circuit can be applied in smoke alarms as well as in other battery-operated equipment. It delivers an output of 30 mA at 9 V from a 1.1-V input, and as much as 90 mA at 9 V from a 1.5-V input. A similar circuit setup for two-cell inputs delivers 30 mA at 9 V from 1.6 V, and a current of 80 mA at 9 V from 3.6 V (Fig. 2).   (View)

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SINE_WAVE_ZERO_CROSSING_DETECTOR

Published:2009/7/16 22:52:00 Author:Jessie

Delivers 10-v pulse that coincides with zero crossings of sine-wave input for most of audio range. Output interval is adjustable.-F. Stevens, Jr., Sine-Wave Zero-Crossing Detector, EEE, 13:11, p 45.   (View)

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CATHODE_FOLLOWER_COUPLING_FOR_MAIN_GATE_MVBR

Published:2009/7/16 22:52:00 Author:Jessie

Triode cathode-followers provide coupling from plate to grid of radar main-gate mvbr. Provides positive unblanking gate.-NBS, Handbook Preferred Circuits Navy Aeronautical Electtonic Equipment, Vol, 1, Electron Tube Circuits, 1963, p N10-2.   (View)

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