| 摘要 |
PURPOSE:To quicken conversion speed and to reduce error due to noise by providing plural input stages for a programmable gain amplifier, and giving an operating current to one of the plural input stages to use the programmable gain amplifier. CONSTITUTION:Transistors (TRs) Q5-Q8 of the programmable gain amplifier 20 constitute a switch to change over two input stages. That is, with a terminal CLK+ at a high level and with a CLK- at a low level, the TR Q7 is turned off and the TR Q8 is turned on. Then the TR Q5 is turned on and the TR Q6 is turned off, and the operating current flows Q1, Q2 side only, the side of input 1 is activated and the side of input 2 is inactivated. With the terminal CLK+ at a low level and with the CLK- at a high level, the operation is converted and only the input 2 is activated. Thus, two input stages are selected. Since the amplifier is not saturated, the constitution such as a clamp diode is not required, and the necessity to form a unity gain amplifier is not required to attain high speed operation.
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