| 摘要 |
PURPOSE:To obtain a variable resistance circuit not causing any distortion even at the input of a large signal by adjusting a threshold voltage of N and P-channel transistors (Tr) so as to select each gate length and gate width. CONSTITUTION:In throwing switches 4, 5 to the position shown in broken lines by a predetermined clock, a control voltage VC is charged in a sampling capaci tor 6 and in throwing the switches to the position shown in solid lines, the charge in the capacitor 6 is moved into a hold capacitor 3 and the polarity is inverted. When the operations above are repeated continuously, the capacitor 3 is charged up to a voltage -VC. A current flowing between terminals is expressed as I=In+Ip, where In, Ip are currents flowing to N and P-channel MOS Trs 1, 2 and V1, V2 are voltages across terminals 7, 8. The distortion component of the current I is eliminated by adjusting the threshold voltage of the Trs 1, 2 and selecting the gate length and gate width to a prescribed value and the resistance value between the terminals 7 and 8 is changed accu rately by using the voltage VC. |
