| 摘要 |
PURPOSE:To obtain circuit not affected with temperature and frequency by applying A/D conversion to an output signal of an analog arithmetic amplifier circuit, and reading a logarithmic transformation value measured and stored accurately in an address corresponding to the output, temperature and frequency from a memory. CONSTITUTION:An amplified output V2 of an analog logarithmic amplifier circuit AL of an input V1 is converted into a digital signal (a) via an A/D converter circuit. Moreover, a temperature detection element is provided near the circuit AL and a temperature code generator TC generates a digital code signal (b) in response to the detected temperature. Furthermore, a digital code generating circuit FC generates a digital code (c) corresponding to the frequency region. Then an accurate logarithmic transformation value is read from a memory MEM the address of which in response to the codes a, b, c the value measured accurately is stored in advance. Thus, the circuit not affected by temperature and frequency is obtained. |
