Patent ID: 8611561
Filing Date: 2013-12-17
Classification: H03F,H03G

Abstract:
1. A first stage amplifier circuit comprising: an input terminal configured to receive an input signal from an external circuit; a first resistor arranged such that a first terminal thereof is connected to the input terminal; a second resistor arranged such that a first terminal thereof is connected to a second terminal of the first resistor; an operational amplifier arranged such that an inverting input terminal thereof is connected to a second terminal of the second resistor, and a reference voltage is applied to a non-inverting input terminal thereof; a third resistor arranged between an output terminal of the operational amplifier and the inverting input terminal of the operational amplifier; a first diode arranged between the second terminal of the first resistor and a first fixed voltage terminal such that a cathode thereof is on the first fixed voltage terminal side; and a second diode arranged between the second terminal of the first resistor and a second fixed voltage terminal such that a cathode thereof is on the second terminal side of the first resistor, wherein the aforementioned components are integrated on a single semiconductor substrate, and wherein an input voltage range of the first stage amplifier circuit is adjustable according to a division ratio provided by the first resistor and the second resistor.