| 摘要 |
An optical sensor system for use in a currency validator is described. The system includes a microcontroller (32), a plurality of light transmitters and light receivers (A, B, C, D, SL, SR, and CC) and a variable gain amplifier circuit (46) connected to the receivers and to the microcontroller (32). The microcontroller (32) controls the gain of the variable gain amplifier circuit (46). The variable gain amplifier circuit (46) includes dual transconductance amplifiers (96, 97) connected together in such a manner to compensate for leakage current over a wide range of temperatures.
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