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Signal Conditioning

Photo Optical Modulator

Photo Optical Modulator: Photo Optical Modulator – The principle of an optical dc chopper is illustrated in Fig. 14.42. Devices of this type have been used widely in infrared signal detectors, whose output is a slowly varying dc product. The properties of the parallel connected photo re­sistor are such that the device produces a decrease …

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Synchronous Vibrator and Synchronous Chopper

Synchronous Vibrator and Synchronous Chopper: Low dc current may be transformed into a high voltage dc by simple chopper action. Although an inductive type transformation process is required, the out­put dc may be obtained without rectifying devices. Figure 14.39 shows a circuit function of a synchronous vibrator. Contacts a and b connect the input dc …

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Varactor Diode Symbol

Varactor Diode Symbol: A specially processed junction diode that assumes the properties of a variable capacitor (about 5 – 250 pf) when its dc reverse voltage is varied is called a Varactor Diode shown in Fig. 14.37. This unique behavior can be used in special modulator circuits designed to turn a low voltage dc signal …

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Transistor Chopper Circuit

Transistor Chopper Circuit: Transistor Chopper Circuit – A single transistor used as a dynamic switch to convert low level dc signal to an ac waveform is shown in Fig. 14.34. If the voltage applied to the tran­sistor base is negative (in the case of a PNP transistor), both emitter and collector diodes are shorted, and …

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Magnetic Modulator

Magnetic Modulator: The most reliable substitutes for electromechanical choppers are magnetic modulators. These devices reach a null stability as low as 10 μV, but their response time is often less than 2 Hz and the ambient temperature range is restricted. The 3-leg saturable reactor, shown in Fig. 14.32 falls within the cat­egory of magnetic modulator …

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Self Oscillating Converter (Transistorized Chopper Circuit)

Self Oscillating Converter (Transistorized Chopper Circuit): Self Oscillating Converter (Transistorized Chopper Circuit) – A Transistorized dc to ac converter suitable for low level dc signal is illustrated in Fig. 14.30. The unique property of this assembly is that it starts to oscillate vigorously at very low levels of dc collector voltages at only a few …

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What is Electromechanical Chopper?

What is Electromechanical Chopper?: Electromechanical Chopper – An ac amplifier must see ac in order to perform useful work. A fair number of chopping and modulation techniques are available to change direct current, or to change very slowly varying signals into square waves (or pulses). Associated circuitry, inserted at the amplification system common output, may …

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Chopper Type DC Amplifier

Chopper Type DC Amplifier: A simple ac amplifier Transformer may be used to amplify a dc input through the use of additional circuit component known as chopper. In this circuit, the dc signal is first converted into an ac signal, amplified by a standard amplifier, and finally converted back to a dc signal. The chopper …

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