Signal Processing

Input_signal_conditioner_for_low_voltage_ADC

Published:2009/7/24 22:08:00 Author:Jessie

Figure 6-40 shows a MAX495 connected as an input signal conditioner for a MAX187 ADC. The MAX495 can operate from either a single supply (+2.7 V to +6 V) or split supplies (±1.35 V to ±3 V). Each op amp requires less than 150 μA supply current, but it can drive a 1-kΩ load. The input-referred voltage noise is 25 nV√Hz, the offset is 200 μV, and the gain-bandwidth is 500 kHz (see Fig. 6-41 for additional pin configurations). MAXIM NEW RELEASES DATA BOOK, 1995, P. 3-23, 3-37.   (View)

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A.C. Time Switch Controller Circuit

Published:2011/7/21 2:02:00 Author:Joyce | Keyword: A.C., Time Switch , Controller

As shown in the figure, the controller includes a depressurization and rectification relay, a monostable timing relay and an ac solid-state relay. The monostable time circuit is composed of 555, R2, RP1, and C4. Press AN, feet 3 of 555 will display a high level to dredge the ac output end of the ac solid-state relay and connect the load, at this time the timing will start .The timing time, namely the stable time of monostability is: td = 1.1 RP1C4.The longest timing time according to the parameters in the figure is about 30 minutes, which can be regulated by adjusting RP1.   (View)

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Simple Crystal Oscillator Test Circuit

Published:2011/7/22 22:16:00 Author:Joyce | Keyword: Simple, Crystal Oscillator , Test

Here is an introduction of a simple crystal oscillation test machine, whose schematic circuit is as shown in the figure attached. In the figure, V1 and its peripheral components (including the crystal oscillator to be tested) compose a capacitance connecting three point type oscillator. When the two ends of probe X1 X2 are connected with the crystal oscillator to be tested, the circuit will start oscillation. Oscillation signal will be output after being amplified by the emitter follower V2. Then it will provide bias current to V3 after being coupled by C4 and voltage-multiplied and rectificated by D1, D2. So V3 will break over and LED will flicker. If the crystal oscillation doesn`t work well or disconnects, the circuit will not start oscillation and LED will not flicker.   (View)

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3-1 Pulse Frequency Dividing Circuit

Published:2011/7/21 0:39:00 Author:Joyce | Keyword: 3-1, Pulse Frequency , Dividing

In digital circuits, sometimes a frequency dividing circuit is needed to subtract a few pluses from an input pulse. Appropriate composition of CD4013 and feedback gate can make almost any circuit combination of pulse subtraction. As shown in the figure is a 3-1 pulse frequency dividing circuit composed of CD4013.   (View)

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High-precision 50Hz Time Base Signal Source Circuit

Published:2011/7/21 1:14:00 Author:Joyce | Keyword: High-precision , 50Hz , Time Base , Signal Source

In some early digital electronic clocks supplied by ac, 50 Hz ac power supply is used as time base signal for second after frequency division because of circuit structure. Since small deviation is inevitable for the frequency of the ac power supply, major deviation from actual time will be created after years later. In order to eliminate the deviation, some amateurs have made various kinds of high precision 50 Hz time base circuits, among which the circuit composed of CD4060 is most commonly used. It is as shown in the figure.   (View)

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HARTLEY_OSCILLATOR

Published:2009/6/29 4:41:00 Author:May

Resonant frequency is 1/2 π √LIC1．   (View)

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2_MHz_OSCILLATOR_

Published:2009/6/29 4:37:00 Author:May

Miller 9055 miniature slugtuned coil；allresistors 1/4W 5％；all caps mln．25 V ceramic.   (View)

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10_MHz_OSCILLATOR

Published:2009/6/29 4:36:00 Author:May

  (View)

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400_MHz_OSCILLATOR_

Published:2009/6/29 4:35:00 Author:May

  (View)

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LOW_DISTORTION_OSCILLATOR

Published:2009/6/29 4:34:00 Author:May

The 2N5485 JFET is capable of oscillating in a circuit where harmonic distortion is very low. The JFET local oscillator is excellent when a low harmonic content is required for a good mixer circuit.   (View)

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500_MHz_OSCILLATOR

Published:2009/6/29 4:33:00 Author:May

  (View)

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800Hz Signal Generator Circuit

Published:2011/7/20 23:42:00 Author:Joyce | Keyword: 800Hz , Signal Generator

The oscillation stage of this 800 Hz signal generator is a transformer coupling LC oscillating circuit, which is simple and has a stable frequency. Control amplifier is used as buffer amplifier to reduce distortion, and potentiometer can be used to adjust the output level. 1. The technical index (1)operating frequency : 800 Hz ; (2) frequency stability:≤士 20 Hz ; (3) output level: 0 dB / 600 Ω. 2. Working principle is as shown in the figure. The 800 Hz signal generator is composed of LC oscillation stage and buffer amplifier stage. Oscillation stage: The tuned transformer T1 is used as LC oscillation tank circuit and output transformer, and C2 is a tuned capacitor.   (View)

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1kHz Audio Square Wave Generator Circuit

Published:2011/7/21 0:20:00 Author:Joyce | Keyword: 1kHz, Audio , Square Wave , Generator

This 1 kHz audio square wave generator is mainly composed of comparator LM324 and R2, R3, R4, C1. The circuit is as shown in the figure. Reference voltage GB / 2 at the input end feet 3 of LM324 is received through bleeder circuit R1, R2. R2, R3 constitute positive feedback, while integrating circuit R4、C1 compose negative feedback .Set the value of R2,R3 to make the following formula work out: R2 / (R2 + R3) = 0.5, and repeat frequency of the square wave is: f = 1/2R4·Cl . If C1 = 0.033 pF,R4 = 15 kΩ, the value of f should be 1kHz. Changing C1 or R4 will change the oscillation frequency.   (View)

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1.8kHz Signal Generator Circuit

Published:2011/7/21 0:30:00 Author:Joyce | Keyword: 1.8kHz , Signal Generator

The circuit in the figure selects temperature coefficient for the best working state and reasonable distribution of the components of the resonance loop. Alternating current and stabilized voltage are used at both ends of the resonance so that excellent output amplitude and frequency stability is received. The working temperature is +25℃-±20℃. Even when the power supply voltage changes in the range of -40% at -24V, the frequency △ f will not be greater than 2Hz,and output level △ dB will not be more than 0.26 dB.   (View)

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2100Hz Signal Generator Circuit

Published:2011/7/22 1:58:00 Author:Joyce | Keyword: 2100Hz, Signal, Generator Circuit

The circuit is as shown in the figure. The 2100 Hz signal generator is composed of oscillation, buffer amplifier and alarm circuit. VT1 and related components constitute the collector tuned oscillator. R1, R2 are bias resistances of VT1 .R3, R4 are emitter resistances which are used to stabilize dc working point. At the same time, R3 also provides negative feedback to improve the performance of the oscillator. C3 is the bypass capacitor of R4, which will reduce the wastage of signals. Coil L3-4 of transformerT1 and capacitance C2 constitute the 2100 Hz oscillation tank circuit. The positive feedback voltage is obtained from coil L1-2.   (View)

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Low Frequncy Signal Generator(2Hz、4Hz、60Hz、120Hz ect) Circuit

Published:2011/7/22 2:08:00 Author:Joyce | Keyword: Low Frequncy , Signal , Generator

Low frequency signal generator can be used to measure the sensitivity, frequency response, frequency compensation and tone control of amplifier circuit. It also can be used to repair low frequency amplifiers. So it is a very useful measuring instrument. It also can be used as signal source of digital clock. According to the practical needs, the user can choose from 8 fixed frequencies output by the signal generator. The output amplitude is divided into two gears: 0 ~ 0.1 V, 0 ~ 1 V which can be adjusted continuously. Principle of the circuit is as shown in the figure. Integrated circuit CD4060 is a 14-level frequency divider installed with oscillator.   (View)

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Low Frequency Oscillation Circuit(Luminescent Circuit ) Based on 555 Time-base Circuit

Published:2011/7/22 2:32:00 Author:Joyce | Keyword: Low Frequency, Oscillation , 555 Time-base

As shown in the figure is a luminescent circuit, in which the two leds will flicker simultaneously under proper functioning. Principle of this circuit is similar to that of 555 audio oscillator ,the difference between them is that the capacity of the capacitance C1 will increase to 4.7μ F. Therefore, the oscillation frequency of the circuit is very low, and the changing speed of the level of feet 3 of NE555 will slow down. When feet 3 outputs a high level, led VD1 and VD2 will be on and flicker. When feet 3 outputs a low level, the two leds will go out.   (View)

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Low Frequency Oscillation Circuit(Luminescent Circuit ) Based on 555 Time-base Circuit Two

Published:2011/7/22 2:47:00 Author:Joyce | Keyword: Low Frequency, Oscillation , 555 Time-base

As shown in the figure is a flasher circuit centering on 555 circuit .LED VD1 and VD2 will flicker alternately under proper functioning. Principle of the circuit is briefly described as follows: Time base circuit NE555 and R1, R2, C1 compose the low frequency oscillator. After the circuit starts oscillation, the level of feet 3 of time base circuit 555 will change. When feet 3 is high level, VD1 will be cut off and it will not flicker, but VD2 will. When feet 3 is low level, VD1 will be on and flicker ,while VD2 will be cut off and stop flickering .So,the two leds will flicker alternatively. Colors of the two LEDs should be red, green or yellow since it would make the difference more obvious.   (View)

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Wien bridge sine wave generator composed of F007

Published:2011/8/1 2:43:00 Author:Ecco | Keyword: Wien bridge , sine wave , generator

Figure shows the Wien bridge sine wave generator circuit. The regulator circuit is the Wien bridge oscillator circuit which is used to achieve steady increases, the oscillation frequency is 1kHz. If it uses coaxial double potentiometer to replace the l.5kΩ resistor of bridge, or changes the capacitor values by band switch, the output frequency can be adjusted. The highest frequency of the circuit is decided by the operational amplifier's frequency characteristics, while the low frequency side requires a larger resistance value, so the requirements of the op amp's input impedance should be as high as possible. Connecting in series with a 30kΩ resistor in a voltage-regulator tube branch, the branch is connected to between the 680Ω and 3.9kΩ resistor in order to make gain changes be not too fast. The use of soft breakdown characteristic regulator can reduce the distortion. Distortion can be up to 0.5%.   (View)

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SUPPRESSING_OSCILLATION

Published:2009/6/28 23:36:00 Author:May

Use of positive feedback to pin 5 of comparatorgives sharp and clean output transitions even with slow triangle-wave inputs, with no possibility of comparator bursting into oscillation near crossing point. Input resistors should not be wirewound.Circuit will handle triangle-wave inputs up to several hundred kilohertz.—P. Lefferts, Overcome Comparator Oscillation Through Use of Careful Design, EDN Magazine, May20, 1978, p 123-124.   (View)

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