Decoder circuit, light-receiving amplifier circuit and optical adapter
A decoder and circuit technology, applied in the field of decoder circuits, can solve problems such as difficulty in shrinking the die
Inactive Publication Date: 2004-12-01
SHARP KK
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Problems solved by technology
[0009] As mentioned above, in the conventional circuit structure, two external input terminals are required, or two comparators (differential amplifiers) are required, and there is a problem that it is difficult to reduce the size of the die
Method used
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[0028] Hereinafter, one embodiment of the present invention will be described with reference to FIG. 1 .
[0029] FIG. 1 is a circuit diagram of a decoder circuit 11 according to an embodiment of the present invention. This decoder circuit 11 is arranged in the integrated circuit of the light-receiving amplifier circuit of the optical pickup for reducing the die size, and it decodes the input voltage Vin applied on the single external input terminal 12 into 2 like on / off. instead of a control output, it is decoded into a control output of 3 or more values and output.
[0030] The decoder circuit 11 includes two transistors Q1 and Q2. The input voltage Vin applied to the single external input terminal 12 is commonly input to the bases of the two transistors Q1 and Q2. The emitter of the P-type transistor Q1 is connected to a high-level Vcc power supply, and the collector serves as the output end of the first control output Vo1. The emitter of the N-type transistor Q2 is co...
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Abstract
A decoder circuit of the present invention, mounted on an integrated circuit, decodes input voltage Vin supplied to a single external input terminal into three or more control outputs, and an object of the present invention is to reduce the size of a chip. The foregoing decoder circuit includes: a P-type transistor in which an emitter is connected to a power source line of high level, a base is connected to the external input terminal, and a collector is an output terminal of a first control output; and an N-type transistor in which an emitter is connected to a power source line of low level, a base is connected to the external input terminal, and a collector is an output terminal of a second control output, and decodes the control outputs to three or more sets of data by carrying out logic operations. Therefore, as compared to the case of using a comparator requiring many transistors, a constant current source, and other elements, one each transistor is required for each of the two control outputs to be generated. This facilitates size reduction of a chip.
Description
technical field [0001] The present invention relates to a decoder circuit suitable for being mounted on a light-receiving amplifier circuit or the like in an optical pickup of an optical disc recording / reproducing device, and particularly capable of switching between three or more operation modes by an input voltage applied to a single external input terminal , and also relates to the above-mentioned light-receiving amplifier circuit and optical pickup (pick-up) using the decoder circuit. Background technique [0002] In order to adapt to writing in CD drives and DVD drives, the light-receiving amplifier circuit in the above-mentioned optical pickup also requires various operation modes corresponding to reading and writing. For example, in order to respond to a small signal during reading and a large signal during writing, it is necessary to switch the gain of the light receiving amplifier in two stages. In particular, for DVD drives, etc., in order to cope with recording m...
Claims
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IPC IPC(8): H03K19/20G11B5/09G11B7/13
CPCG11B7/13
Inventor 河村克之白坂康之
Owner SHARP KK