Current mirror

Abstract

Abstract In generators for generating several bias-voltage potentials in integrated circuits comprising current balancing circuits, relatively high voltage drops across the current source are necessary because of the series-connections of several transistors and because of the threshold voltages which are increased due to the substrate control effect in MOS circuits, so that the transistors do not move out of saturation and the output impedance is greatly reduced for this reason. A current balancing circuit is required which, with high accuracy of the current balancing, requires a low voltage drop across the current balancing circuit output. The current balancing circuit contains in the circuit for a reference current (IRef1) a constant current source (Q) and a first transistor (T1). The circuit for a balanced current (I01) contains a second transistor (T2). The bases or gates of these transistors (T1, T2) are connected to one another and to the junction of the current source (Q) and first transistor (T1) (L1). The second transistor (T2) is preceded by a third transistor (T3) as a variable resistor or controlled current source. A differential amplifier (D1) compares the potentials at the junction of the constant current source (Q) and the first transistor (T1) and at the junction between the second and third transistor (T2, T3) and, using the result, controls the third transistor (T3) via its base or via its gate, respectively. The current balancing circuit is suitable for generators for bias-voltage potentials in integrated circuits. <IMAGE>

Inventors

• 👤 Wilhelm Dipl.-Ing. König

Bibliographic Details