Patent ID: 6133763
Filing Date: 2000-10-17
Classification: H03F,H03H

Abstract:
A high impedance circuit, comprising:a first transistor;a first resistance element connected between a collector of the first transistor and a first voltage power supply line;a first current source connected between an emitter of the first transistor and a second power supply line (ground);a second transistor having a same conductivity as the first transistor;a second resistance element connected between a collector of the second transistor and the first voltage power supply line and having a resistance value same as that of the first resistance element;a second current source connected between an emitter of the second transistor and the second power supply line (ground) and being equal to the first current source;a third resistance element connected between the emitter of the first transistor and the emitter of the second transistor;a third transistor, having a base connected to a collector of the second transistor and an emitter connected to a base of the first transistor, said third transistor having the same conductivity of the first transistor;a third current source circuit connected between an emitter of the third transistor and the second power supply line (ground);a first buffer circuit element connected between a collector of the second transistor and a control terminal of the first transistor; anda second buffer circuit element connected between a collector of the first transistor and a control terminal of the second transistor.said second buffer circuit further comprising a fourth transistor, having a base connected to a collector of the first transistor and an emitter connected to a base of the second transistor, said fourth transistor having the same conductivity of the second transistor;a fourth current source circuit connected between an emitter of the fourth transistor and the second power supply line (ground), said fourth current source circuit being equal to said third current source circuit;wherein said third resistance element has a resistance value being twice as high as either first or second resistance elements.