ADJUSTABLE RESISTANCE DEVICE WITH CONTROL CIRCUIT

摘要

An adjustable resistance device having a first parallel arrangement (1) of a first resistor and a first positive-feedback transconductor is provided with a control circuit (20) for controlling the controllable resistance section in the first parallel arrangement (1), which control circuit (20) includes a control loop including a second parallel arrangement (2) which is a copy of the first parallel arrangement (1). The control circuit (20) controls the controllable section of the second parallel arrangement (2) in such a manner that the negative resistance value formed by a second transconductor is substantially equal in magnitude to the resistance value of a second resistor, so that the second parallel arrangement (2) is bistable in the transition range. By selecting the positive resistance value in the first parallel arrangement (1) to be a factor smaller than the negative resistance value, which factor can be realized accurately in an integrated circuit, it is possible to obtain a higher effective resistance with a smaller spread.