| 摘要 |
PURPOSE:To convert a digital signal into an analog signal with high accuracy by providing a charge control circuit connected between an inverting input and an output of an operational amplifier and a switch control circuit controlling the charge control circuit. CONSTITUTION:A switch control circuit 6 receives a digital signal from a terminal 61 and a 2-phase clock signal phi to form a signal controlling the switching of each switch of the charge control circuit 1. A reset pulse generating circuit 69 outputs a reset signal phiR at the initial state to close a switch 16 and the inverting input and the output 18 of the operational amplifier 11 are short- circuited to reduce an output voltage V1 to '0'. Then a control signal S1 is outputted from the circuit 6 to turn on a switch 51 and a switch 41 is turned on by a clock pulse phi and a capacitor 21 is charged by a reference voltage Vr. The switch 16 is turned off by the next pulse phi', switches 31, 32 are turned on and capacitors 21, 22 are connected in parallel. The output V1 of the amplifier 11 is made equal to a terminal voltage of the capacitor 22.
|
