| 摘要 |
PURPOSE: To obtain a logarithmic detector having a large logarithmic linearity range by constituting the detector through appropriate combination of three sets of bipolar transistor pairs and current sources. CONSTITUTION: A logarithmic detector 10 is connected with an amplifier 11. Signals on a line 12 before the amplification by means of the amplifier 11 are supplied to the detector 10 along a pair of lines 14A and 14B and, on the other hand, output signals on a line 13 after amplification are supplied to the detector 10 along a pair of lines 15A and 15B. The detector 10 has two pairs of input lines 16A and 16B and 17A and 17B and a pair of output lines 18A and 18B. In addition, the bases of transistors 25 and 26 are respectively connected to the input lines 16A and 16B and the emitters of the transistors 25 and 26 are connected to a ground by means of a current source 28 which makes a current IT to flow to the ground respectively through impedances 35 and 36. Since the circuit of the detector 10 has a symmetric property, the input line pairs 16 and 17 can be exchanged and inverted without giving any influence to the output of the detector 10. |
