| 摘要 |
PURPOSE:To obtain an amplifier whose gain is changed without using a PN diode and a MOS diode by providing plural capacitive elements and a switch means selecting the capacitive component between an inverting input and an output section of an operational amplifier. CONSTITUTION:An input terminal 1 receiving an input signal VIN is connected to the inverting input of an operational amplifier 3 via a switch S1 closed by a clock phi1 and a switch S4 closed by a clock phi2 and a capacitive component C1. A series connection comprising a capacitive component C2 and a switch S6, a series connection comprising a capacitive component C3 and a switch S7 and a switch S8 are connected in parallel between the inverting input section and the output section of the operational amplifier 3. Comparators 4, 5 compare the voltage of a sampling capacitor C0 with reference voltages V1, -V1 in response to the clock phi2 and outputs alpha, beta control switches S6, S7, S9, S10, S12. The gain depends on the capacitance ratio of the capacitive components C1-C3. Thus, an excellent variable gain amplifier for a CMOS integrated circuit is obtained. |
