This section provides overview, applications, and principles of isolation amplifiers. Also, please take a look at the list of 21 isolation amplifier manufacturers and their company rankings.
Isolation amplifier is amplifiers that can transmit signals while electrically isolating between input and output signals.
They are generally used in measuring instruments and medical equipment because they can be built into the input and output circuits of printed circuit boards, such as microcomputer control boards, to DC-isolate incoming signals from the outside and accurately perform measurements. They also serve to ensure the safety of the user.
Features include prevention of electric shock, signal bifurcation (liability demarcation), measures against high ground potentials, and noise suppression.
Used in heavy electric machinery, industrial machinery, power supply equipment, power generation equipment, medical equipment, semiconductor manufacturing equipment, transportation equipment (vehicles), communication equipment, and measuring equipment.
By incorporating them into circuits at key points, they function as a safety measure to prevent users from receiving electric shocks in the event of equipment malfunctions. When sending signals to multiple systems, multiple use of these devices prevents interference between systems. They also protects the power supply by eliminating reverse current caused by high ground potential. A bonus point is that they can be installed in environments with many noise sources.
The input to be measured is input to a buffer circuit (1) with a very high input impedance that does not affect the signal source. The same voltage as the input signal appears at the output side, and the output of the buffer circuit ① is transmitted to the primary side of the signal transformer, whose output impedance is so low that the output voltage does not fluctuate even if the impedance of the signal transformer changes. The primary and secondary sides of the signal transformer are simultaneously turned on and off repeatedly by switching elements (1) and (2), and a voltage equal to the signal voltage entering the primary side is applied to the capacitor connected to the secondary side based on the principle of synchronous rectification. This voltage is output via a buffer circuit (2) with a very high input impedance so that it is not reduced by the capacitor discharge. The output impedance of the buffer circuit (2) is very low so that the output voltage is not affected by the input impedance of the side loading the output signal. The oscillator frequency is set to match the frequency response of the isolation amplifiers. The performance of this amplifier is greatly affected by the design and quality of the signal transformer.
This section describes the circuit diagram of the isolation amplifiers. Isolation amplifiers are a type of amplifier (amplifier) that operates circuits while completely separating and isolating them so that both circuits are not affected by GND or power supply commonality.
The most standard isolation amplifiers circuit configuration is an optically coupled isolation amplifiers in which the input and output are both analog signals. Here, optical coupling is an isolation-compatible circuit method that isolates using an optical semiconductor with built-in LEDs, such as a photocoupler.
As the flow of the circuit operation, the input analog signal is first converted into encoded digital signal code data by an encoder and a circuit that converts the analog signal on the primary side into a digital signal, and then transmitted optically to the output side by an LED. In the secondary circuit, the signal is received by a photodiode, demodulated by a transimpedance amplifier and a decoder circuit, and converted to an analog signal by a circuit that converts the digital signal to an analog signal and a decoder circuit. The final analog output signal is obtained by a circuit that converts the digital signal into an analog signal and a low-pass filter that removes high-frequency signals such as noise and passes only the necessary low-frequency signals.
Isolation amplifiers photocouplers are optical ICs used in isolation amplifiers circuits, which are used when making an isolated circuit in which the input and output are completely floating above each other, or when detecting signals of different potentials.
Isolation amplifiers with built-in photocouplers are often used to isolate input and output circuits, and are commercially available from a variety of manufacturers. For example, the linear photocoupler LIA 100 is a low-cost, relatively easy-to-produce isolation amplifiers. The ADuM series from Analog Devices, Inc. 25°C and in the 400 kHz bandwidth. It is an excellent product with an accuracy of 1% or better. Other products include the Toshiba TLP7920 and the Renesas RV 1S9353A, and other Japanese manufacturers also have a wide lineup of isolation amplifiers ICs. The lineup of isolation amplifiers ICs is abundant, and we believe that the optimum component for each operating condition should be selected.
*Including some distributors, etc.
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