| 摘要 |
PROBLEM TO BE SOLVED: To easily and surely compensate offset voltages of operational amplifiers in the device of an automatic piano or the like in which operational amplifiers, an A/D converter and a CPU or the like are used. SOLUTION: A zero voltage is applied to amplifiers (operational amplifiers) 226-1 to 226-8 every one minute under the control of a CPU 201. Output voltages (offset voltages) at that time are converted into digital values via an converter 223 to be stored in the RAM connected to the CPU 201. From then on, offset voltages are subtracted from the output of the converter 223 in the CPU 201. |
