Isolated signal transmitting device, isolated signal transmitting circuit and receiving circuit thereof

摘要

An isolated signal transmitting device, an isolated signal transmitting circuit and an isolated receiving circuit thereof are provided to transmit analog signals and digital signals not commonly grounded. The isolated signal transmitting device adapts one current loop for transmitting the analog signals and the digital signals in two opposite directions. The isolated signal transmitting device has two optical couplers to isolate an input and an output of the isolated signal transmitting device not commonly grounded, and the coupled analog signals and the coupled digital signals have respective outputs. Then a user can determine whether the signal is digital or not according to the respective output.

主权项

1. An isolated signal transmitting circuit, comprising:
an analog signal input; a digital signal input; a first cross port; a second cross port; a first operational amplifier, comprising a positive input, a negative input and an output; wherein the positive input is grounded, the negative input is electronically connected to the first cross port and also connected to the analog signal input through a first resistor, and the output is electronically connected to the second cross port; a metal-oxide-semiconductor field-effect transistor (MOSFET), comprising a gate, a source and a drain; wherein the source is electronically connected to a power input negative terminal and also connected to the gate through a third resistor, and the drain is electronically connected to the negative input of the first operational amplifier through a fourth resistor; a PNP current mirror, comprising:
a first PNP transistor, comprising an emitter, a base and a collector;wherein the emitter is electronically connected to a power input positive terminal, and the base is electronically connected to the collector;a second PNP transistor, comprising an emitter, a base and a collector;wherein the emitter of the second PNP transistor is electronically connected to the power input positive terminal, the base of the second PNP transistor is electronically connected to the base of the first PNP transistor, and the collector of the second PNP transistor is electronically connected to the gate of the MOSFET; andan eighth resistor electronically connected between the collector of the first PNP transistor and the digital signal input.