| 摘要 |
PURPOSE:To constitute a D/A converter with integrated circuits even if a resistor pattern is not prepared, by constituting a load resistor for forming analog voltage to be connected to the input side of an operational amplifier with MOS transistors (TRs). CONSTITUTION:Drains of N channel MOS TRs (NMOS)QN1-QN4 and P channel MOS TRs (PMOS)QP1-QP4 are connected mutually and the connecting points are connected to a reference voltage VREP. The source of the NMOSQN1- QN4 are grounded and the source of the PMOSQP1-QP4 is connected to an inverting input of an operational amplifier A. The gates of the NMOS and PMOS are mutually connected and signals b1-b4 in 2<0>-2<3> are applied. The gate width of the PMOSQP1-QP4 is set to 1:2:4:8 to obtain the resistances as 1:1/2:1/4:1/8. For example, when the signal b1 is 1 and the signals b2-b4 are 0, the NMOSQN1 and PMOSQP2-QP4 are turned off, the PMOSQP1, NMOSQN2-QN4 are turned on, and only the on-resistance of the PMOSQP1 is connected to the amplifier A and an analog signal corresponding to 0001 is outputted from the amplifier A. |
