Differential optocoupler amplifier with low noise, low power and balanced output

Abstract

An optocoupler with differential input and balanced output was realized to make galvanic decoupling of a particle detector located in a high common mode disturbance environment. The circuit configuration incorporates a true differential optocoupled feedback, with low bias current in LEDs and photodiodes. The present circuit improves by a factor two the dynamic range of a previous solution. Large Common Mode (CMRR) and Power Supply (PSRR) Rejection Ratio, low crossover distortion, high dynamic range, low noise and power dissipation have been achieved.

A linear, low-noise, low-power optocoupler amplifier for bolometric detectors

“…Instead, the circuit of Fig. 1 allows to obtain bipolar operation, although a very small bias current is used for biasing [4] If I "+6 is the maximum current each photodiode can handle, while » is the maximum expected input signal, we have I " "» /R . The maximum signal-to-noise ratio, the dynamic range, (S/N) +6 , results:…”

A linear optical coupler for cryogenic detectors

“…The schematic circuit of the optical coupler, OPC, presented is very similar to the one in Ref. [3], which is an improved version of a "rst implementation [4]. The principle of operation of an analog OPC based on the photodiode}LED} photodiode combination is quite simple.…”

“…The class AB operation refers to the way the two chips are biased, with very low current induced by the voltage supplies $< 0#$ . The voltage < !2 is an active ground that generates a signal in opposition to the input signal, allowing to double the dynamic at the operational ampli"er, OA, output, < [3]. This in turn permits to use a value for the resistors R which is of what should be used in the case < !2 were not present, with a reduction of input noise of a factor close to two.…”

“…With this device we have realized a circuit based on the one described in Ref. [3], but with di!erent OA needed to realize the structure, the Elantec EL2444. The EL2444 is a quad-high-speed OA having a bipolar pair as input transistors.…”

Electrothermal model of optocoupler for SPICE

“…Optocouplers are very often used in many electronic and power electronic circuits, since they assure simple galvanic separation of two circuits [1][2][3][4][5][6][7][8][9][10], e.g. an input circuit from a power circuit in dc-dc converters [1,2,4,6,7,9,10].…”